some pair management changes, allow to choose pair cache at run-time.

src/BulletCollision/BroadphaseCollision/btSimpleBroadphase.cpp

@@ -45,7 +45,7 @@ btSimpleBroadphase::btSimpleBroadphase(int maxProxies, btOverlappingPairCache* o
 	if (!overlappingPairCache)
 	{
 		void* mem = btAlignedAlloc(sizeof(btOverlappingPairCache),16);
-		m_pairCache = new (mem)btOverlappingPairCache();
+		m_pairCache = new (mem)btHashedOverlappingPairCache();
 		m_ownsPairCache = true;
 	}