- 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/ComputeUVMappingProcess.cpp

@@ -495,7 +495,7 @@ void ComputeUVMappingProcess::Execute( aiScene* pScene)
 
 					// Update the material property list
 					mapping = aiTextureMapping_UV;
-					((MaterialHelper*)mat)->AddProperty(&idx,1,AI_MATKEY_UVWSRC(prop->mSemantic,prop->mIndex));
+					((aiMaterial*)mat)->AddProperty(&idx,1,AI_MATKEY_UVWSRC(prop->mSemantic,prop->mIndex));
 				}
 			}
 		}