work on pybullet/C-API createMultiBody (still preliminary, only sphere/box collision shapes, no links/hierarchies yet, soon)

pybullet/C-API, expose linear/angular damping
fix some warnings (param name needs to be same in .h and .cpp)
fix potential startup threading issue (args were deleted in main thread while still possibly use in child thread)
fix for spinning/rolling friction in case of mixing maximal and reduced coordinate btMultiBody+btRigidBody

src/BulletDynamics/Featherstone/btMultiBody.cpp

@@ -2013,10 +2013,10 @@ const char*	btMultiBody::serialize(void* dataBuffer, class btSerializer* seriali
 		}
 		mbd->m_links = mbd->m_numLinks? (btMultiBodyLinkData*) serializer->getUniquePointer((void*)&m_links[0]):0;
 
-		// Fill padding with zeros to appease msan.
-#ifdef BT_USE_DOUBLE_PRECISION
-		memset(mbd->m_padding, 0, sizeof(mbd->m_padding));
-#endif
-
+		// Fill padding with zeros to appease msan.
+#ifdef BT_USE_DOUBLE_PRECISION
+		memset(mbd->m_padding, 0, sizeof(mbd->m_padding));
+#endif
+
 		return btMultiBodyDataName;
 }