Make .bullet serialization mode robust:

Deal with broken DNA serialization. Bullet 2.76 release revision 2035 - 2046 was broken, and this includes the Maya Dynamica plugin.
Added some workaround to deal with the broken .bullet files, instead of crashing.

src/BulletCollision/CollisionShapes/btStridingMeshInterface.h

@@ -104,7 +104,11 @@ struct	btIntIndexData
 	int	m_value;
 };
 
-
+struct	btShortIntIndexData
+{
+	short m_value;
+	char m_pad[2];
+};
 
 struct	btShortIntIndexTripletData
 {
@@ -121,6 +125,8 @@ struct	btMeshPartData
 	btIntIndexData				*m_indices32;
 	btShortIntIndexTripletData	*m_3indices16;
 
+	btShortIntIndexData			*m_indices16;//backwards compatibility
+
 	int                     m_numTriangles;//length of m_indices = m_numTriangles
 	int                     m_numVertices;
 };