Share btGjkPairDetector, btGjkEpa2, btVoronoiSimplexSolver with SPU/Multithreaded implementation (remove duplicate code)

Make btTypedConstraint and btPersistentManifold both derive from btTypedObject to make SPU-side generic constraint solver easier.

Note: all build systems need to be updated: remove SpuVoronoiSimplexSolver.cpp, SpuGjkPairDetector.cpp, SpuEpaPenetrationDepthSolver.cpp, SpuGjkEpa2.cpp

src/BulletCollision/NarrowPhaseCollision/btPersistentManifold.cpp

@@ -25,7 +25,8 @@ ContactProcessedCallback	gContactProcessedCallback = 0;
 
 
 btPersistentManifold::btPersistentManifold()
-:m_body0(0),
+:btTypedObject(BT_PERSISTENT_MANIFOLD_TYPE),
+m_body0(0),
 m_body1(0),
 m_cachedPoints (0),
 m_index1a(0)