support diamondsubdivision (thanks Jay for contribution)

support user-defined broadphase collision filtering (thanks Marten)
make sure btSimpeDynamicsWorld doesn't use cache friendly optimization in the solver (added an assert, and updated BasicDemo)

src/BulletCollision/BroadphaseCollision/btOverlappingPairCache.cpp

@@ -24,7 +24,8 @@ subject to the following restrictions:
 int	gOverlappingPairs = 0;
 
 btOverlappingPairCache::btOverlappingPairCache():
-m_blockedForChanges(false)
+m_blockedForChanges(false),
+m_overlapFilterCallback(0)
 //m_NumOverlapBroadphasePair(0)
 {
 }