assign proper index when removing a child shape from btCompoundShape

Thanks to sparkprime for the report and fix in Issue 354
See http://code.google.com/p/bullet/issues/detail?id=354
Fix a few warnings

src/BulletCollision/CollisionDispatch/btCompoundCollisionAlgorithm.cpp

@@ -114,7 +114,9 @@ public:
 
 	void	ProcessChildShape(btCollisionShape* childShape,int index)
 	{
-		
+		btAssert(index>=0);
+		btAssert(index<compoundShape->getNumChildShapes());
+
 		btCompoundShape* compoundShape = static_cast<btCompoundShape*>(m_compoundColObj->getCollisionShape());