Misc. typos

Some are doxy comments, some are just trivial source comment typos. 
Found using `codespell -q 3 --skip="./contrib" -I ../assimp-whitelist.txt`
whereby whitelist contained:
```
childs
iff
lod
nto
ot
whitespaces
```

code/AMFImporter.hpp

@@ -249,7 +249,7 @@ private:
 
 	/// \fn size_t PostprocessHelper_GetTextureID_Or_Create(const std::string& pID_R, const std::string& pID_G, const std::string& pID_B, const std::string& pID_A)
 	/// Return converted texture ID which related to specified source textures ID's. If converted texture does not exist then it will be created and ID on new
-	/// converted texture will be returned. Convertion: set of textures from \ref CAMFImporter_NodeElement_Texture to one \ref SPP_Texture and place it
+	/// converted texture will be returned. Conversion: set of textures from \ref CAMFImporter_NodeElement_Texture to one \ref SPP_Texture and place it
 	/// to converted textures list.
 	/// Any of source ID's can be absent(empty string) or even one ID only specified. But at least one ID must be specified.
 	/// \param [in] pID_R - ID of source "red" texture.
@@ -378,7 +378,7 @@ private:
 	void XML_CheckNode_MustHaveChildren();
 
 	/// \fn bool XML_CheckNode_NameEqual(const std::string& pNodeName)
-	/// Chek if current node name is equal to pNodeName.
+	/// Check if current node name is equal to pNodeName.
 	/// \param [in] pNodeName - name for checking.
 	/// return true if current node name is equal to pNodeName, else - false.
 	bool XML_CheckNode_NameEqual(const std::string& pNodeName) { return mReader->getNodeName() == pNodeName; }

code/AMFImporter_Node.hpp

@@ -137,7 +137,7 @@ struct CAMFImporter_NodeElement_Instance : public CAMFImporter_NodeElement
 {
 	/****************** Variables ******************/
 
-	std::string ObjectID;///< ID of object for instanciation.
+	std::string ObjectID;///< ID of object for instantiation.
 	/// \var Delta - The distance of translation in the x, y, or z direction, respectively, in the referenced object's coordinate system, to
 	/// create an instance of the object in the current constellation.
 	aiVector3D Delta;

code/ColladaExporter.cpp

@@ -1561,7 +1561,7 @@ void ColladaExporter::WriteNode( const aiScene* pScene, aiNode* pNode)
     for( size_t a = 0; a < pNode->mNumMeshes; ++a )
     {
         const aiMesh* mesh = mScene->mMeshes[pNode->mMeshes[a]];
-        // do not instanciate mesh if empty. I wonder how this could happen
+        // do not instantiate mesh if empty. I wonder how this could happen
         if( mesh->mNumFaces == 0 || mesh->mNumVertices == 0 )
             continue;
 

code/ColladaHelper.h

@@ -302,7 +302,7 @@ struct Accessor
     size_t mOffset;  // in number of values
     size_t mStride;  // Stride in number of values
     std::vector<std::string> mParams; // names of the data streams in the accessors. Empty string tells to ignore.
-    size_t mSubOffset[4]; // Suboffset inside the object for the common 4 elements. For a vector, thats XYZ, for a color RGBA and so on.
+    size_t mSubOffset[4]; // Suboffset inside the object for the common 4 elements. For a vector, that's XYZ, for a color RGBA and so on.
                           // For example, SubOffset[0] denotes which of the values inside the object is the vector X component.
     std::string mSource;   // URL of the source array
     mutable const Data* mData; // Pointer to the source array, if resolved. NULL else

code/ColladaLoader.cpp

@@ -1619,7 +1619,7 @@ void ColladaLoader::FillMaterials( const ColladaParser& pParser, aiScene* /*pSce
         mat.AddProperty( &effect.mRefractIndex, 1, AI_MATKEY_REFRACTI);
 
         // transparency, a very hard one. seemingly not all files are following the
-        // specification here (1.0 transparency => completly opaque)...
+        // specification here (1.0 transparency => completely opaque)...
         // therefore, we let the opportunity for the user to manually invert
         // the transparency if necessary and we add preliminary support for RGB_ZERO mode
         if(effect.mTransparency >= 0.f && effect.mTransparency <= 1.f) {

code/ColladaParser.cpp

@@ -224,7 +224,7 @@ void ColladaParser::ReadStructure()
 }
 
 // ------------------------------------------------------------------------------------------------
-// Reads asset informations such as coordinate system informations and legal blah
+// Reads asset information such as coordinate system information and legal blah
 void ColladaParser::ReadAssetInfo()
 {
     if( mReader->isEmptyElement())

code/ColladaParser.h

@@ -77,7 +77,7 @@ namespace Assimp
         /** Reads the structure of the file */
         void ReadStructure();
 
-        /** Reads asset informations such as coordinate system informations and legal blah */
+        /** Reads asset information such as coordinate system information and legal blah */
         void ReadAssetInfo();
 
         /** Reads the animation library */

code/LWOMaterial.cpp

@@ -483,7 +483,7 @@ void LWOImporter::FindVCChannels(const LWO::Surface& surf, LWO::SortedRep& sorte
         const LWO::VColorChannel& vc = layer.mVColorChannels[i];
 
         if (surf.mVCMap == vc.name) {
-            // The vertex color map is explicitely requested by the surface so we need to take special care of it
+            // The vertex color map is explicitly requested by the surface so we need to take special care of it
             for (unsigned int a = 0; a < std::min(next,AI_MAX_NUMBER_OF_COLOR_SETS-1u); ++a) {
                 out[a+1] = out[a];
             }

code/LWSLoader.cpp

@@ -471,7 +471,7 @@ void LWSImporter::BuildGraph(aiNode* nd, LWS::NodeDesc& src, std::vector<Attachm
 // Determine the exact location of a LWO file
 std::string LWSImporter::FindLWOFile(const std::string& in)
 {
-    // insert missing directory seperator if necessary
+    // insert missing directory separator if necessary
     std::string tmp;
     if (in.length() > 3 && in[1] == ':'&& in[2] != '\\' && in[2] != '/')
     {

code/ObjExporter.cpp

@@ -155,7 +155,7 @@ std::string ObjExporter :: GetMaterialLibName()
 
 // ------------------------------------------------------------------------------------------------
 std::string ObjExporter::GetMaterialLibFileName() {
-    // Remove existing .obj file extention so that the final material file name will be fileName.mtl and not fileName.obj.mtl
+    // Remove existing .obj file extension so that the final material file name will be fileName.mtl and not fileName.obj.mtl
     size_t lastdot = filename.find_last_of('.');
     if (lastdot != std::string::npos)
         return filename.substr(0, lastdot) + MaterialExt;

code/OgreMaterial.cpp

@@ -258,7 +258,7 @@ aiMaterial* OgreImporter::ReadMaterial(const std::string &pFile, Assimp::IOSyste
                 ReadTechnique(Trim(techniqueName), ss, material);
             }
 
-            // Read informations from a custom material
+            // Read information from a custom material
             /** @todo This "set $x y" does not seem to be a official Ogre material system feature.
                 Materials can inherit other materials and override texture units by using the (unique)
                 parent texture unit name in your cloned material.

code/TextureTransform.cpp

@@ -317,7 +317,7 @@ void TextureTransformStep::Execute( aiScene* pScene)
                     info.lockedPos = AI_TT_UV_IDX_LOCK_TBD;
                 }
 
-                // Get all coresponding meshes
+                // Get all corresponding meshes
                 for (unsigned int n = 0; n < pScene->mNumMeshes;++n)    {
                     aiMesh* mesh = pScene->mMeshes[n];
                     if (mesh->mMaterialIndex != i || !mesh->mTextureCoords[0])

code/X3DExporter.hpp

@@ -27,7 +27,7 @@ namespace Assimp
 ///
 /// Pay attention that X3D is format for interactive graphic and simulations for web browsers. aiScene can not contain all features of the X3D format.
 /// Also, aiScene contain rasterized-like data. For example, X3D can describe circle all cylinder with one tag, but aiScene contain result of tesselation:
-/// vertices, faces etc. Yes, you can use algorithm for detecting figures or shapes, but thats not good idea at all.
+/// vertices, faces etc. Yes, you can use algorithm for detecting figures or shapes, but that's not a good idea at all.
 ///
 /// Supported nodes:
 ///		Core component:
@@ -96,7 +96,7 @@ private:
 	aiMatrix4x4 Matrix_GlobalToCurrent(const aiNode& pNode) const;
 
 	/// \fn void AttrHelper_CommaToPoint(std::string& pStringWithComma)
-	/// Convert commas in string to points. Thats need because "std::to_string" result depend on locale (regional settings).
+	/// Convert commas in string to points. That's needed because "std::to_string" result depends on locale (regional settings).
 	/// \param [in, out] pStringWithComma - reference to string, which must be modified.
 	void AttrHelper_CommaToPoint(std::string& pStringWithComma) { for(char& c: pStringWithComma) { if(c == ',') c = '.'; } }
 

code/X3DImporter.hpp

@@ -176,7 +176,7 @@ namespace Assimp {
 /// Ignored attributes: "creaseAngle", "convex", "solid".
 ///
 /// Texture coordinates generating: only for Sphere, Cone, Cylinder. In all other case used PLANE mapping.
-///		It's better that Assimp main code has powerfull texture coordinates generator. Then is not needed to
+///		It's better that Assimp main code has powerful texture coordinates generator. Then is not needed to
 ///		duplicate this code in every importer.
 ///
 /// Lighting limitations.
@@ -401,10 +401,10 @@ private:
 	/************** Functions: XML set *************/
 	/***********************************************/
 
-	/// Chek if current node is empty: <node />. If not then exception will throwed.
+	/// Check if current node is empty: <node />. If not then exception will throwed.
 	void XML_CheckNode_MustBeEmpty();
 
-	/// Chek if current node name is equal to pNodeName.
+	/// Check if current node name is equal to pNodeName.
 	/// \param [in] pNodeName - name for checking.
 	/// return true if current node name is equal to pNodeName, else - false.
 	bool XML_CheckNode_NameEqual(const std::string& pNodeName) { return mReader->getNodeName() == pNodeName; }

code/glTF2Exporter.cpp

@@ -56,7 +56,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <assimp/material.h>
 #include <assimp/scene.h>
 
-// Header files, standart library.
+// Header files, standard library.
 #include <memory>
 #include <inttypes.h>
 

code/glTFExporter.cpp

@@ -56,7 +56,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <assimp/material.h>
 #include <assimp/scene.h>
 
-// Header files, standart library.
+// Header files, standard library.
 #include <memory>
 #include <inttypes.h>