- 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/FindInvalidDataProcess.h

@@ -56,7 +56,7 @@ namespace Assimp	{
  *
  *  Originally this was a workaround for some models written by Blender
  *  which have zero normal vectors. */
-class ASSIMP_API FindInvalidDataProcess 
+class FindInvalidDataProcess 
 	: public BaseProcess
 {
 public: