remove speculative contacts, they break restitution and cause other artifacts

use btConvexPolyhedron for debug rendering, if available
fixes in btConvexConvexAlgorithm for polyhedral contact clipping, if GJK separating normal is zero
don't shift vertices in btPolyhedralConvexShape

src/LinearMath/btQuickprof.cpp

@@ -276,7 +276,8 @@ CProfileNode::CProfileNode( const char * name, CProfileNode * parent ) :
 	RecursionCounter( 0 ),
 	Parent( parent ),
 	Child( NULL ),
-	Sibling( NULL )
+	Sibling( NULL ),
+	m_userPtr(0)
 {
 	Reset();
 }