- 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/TextureTransform.cpp

@@ -236,7 +236,7 @@ void TextureTransformStep::Execute( aiScene* pScene)
 				// Setup a shortcut structure to allow for a fast updating
 				// of the UV index later
 				TTUpdateInfo update;
-				update.mat = (MaterialHelper*) mat;
+				update.mat = (aiMaterial*) mat;
 				update.semantic = prop->mSemantic;
 				update.index = prop->mIndex;