- extract MaterialHelper and move all of its members to aiMaterial in /include.

- pull in IOhannes' patch to set the gcc default visibility for all symbols to NO and to mark ASSIMP_API with __attribute__ ((visibility("default"))).
- drop unneeded ASSIMP_API from most internal classes in /code, we just need to keep some exports on Windows to keep AssimpView alive.

git-svn-id: https://assimp.svn.sourceforge.net/svnroot/assimp/trunk@1066 67173fc5-114c-0410-ac8e-9d2fd5bffc1f

code/SkeletonMeshBuilder.cpp

@@ -253,7 +253,7 @@ aiMesh* SkeletonMeshBuilder::CreateMesh()
 // Creates a dummy material and returns it.
 aiMaterial* SkeletonMeshBuilder::CreateMaterial()
 {
-	Assimp::MaterialHelper* matHelper = new Assimp::MaterialHelper;
+	aiMaterial* matHelper = new aiMaterial;
 
 	// Name
 	aiString matName( std::string( "SkeletonMaterial"));