make btHashMap data protected (not private) for easier serialization

move btTriangleInfoMap.h into its own header, into the BulletCollision/CollisionShapes folder
add btTriangleInfoMap pointer to btBvhTriangleMeshShape, so we don't need to use the 'userpointer' anymore
preparation for serialization of btTriangleInfoMap.

See also http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=4603&start=30

src/LinearMath/btHashMap.h

@@ -199,6 +199,7 @@ template <class Key, class Value>
 class btHashMap
 {
 
+protected:
 	btAlignedObjectArray<int>		m_hashTable;
 	btAlignedObjectArray<int>		m_next;