Assimp patch

We contribute our improvements back to original projects, however, recent improvements may still be present only in Lightsprint SDK.

Accepted patches

• Fix of .obj crash (https://github.com/assimp/assimp/blob/master/CREDITS).
• Fix of memory leak (https://sourceforge.net/tracker/index.php?func=detail&aid=3134561&group_id=226462&atid=1067632)
• Fix of VS2010 compilation (rev 993)
• several more, see assimp on github