Merged revisions 2622:2663 from branch 1.6. SMaterial bug, MS3D patch, LWO fix. Better Shift recognition under 2in32. D3D depth buffer MSAA problems fixed. string<c16> changed to io::path. Fix 2dimagebatch, add better mtl file finder. Fix some OpenGL extension checks. Fixed x86-64 warnings. Export symbols in gcc4. Scolling in GUITab fixed. Fixed PixelBlend16 and SW driver. FPS cam stuttering fixed. OSX project additions. New scene parameter to ignore obj's mtl files.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2664 dfc29bdd-3216-0410-991c-e03cc46cb475