Fix memory leak due to batchRayCast never deleting the btTaskScheduler.

(and issue with TaskScheduler/btTaskScheduler.cpp, add JobQueue::exit, call it first, since it uses the m_threadSupport which was deleted before the destrucor was called.
Use a hashmap to store user timers, to avoid allocating many identical strings.

examples/SharedMemory/PhysicsLoopBack.cpp

@@ -247,3 +247,11 @@ void PhysicsLoopBack::getUserDataInfo(int bodyUniqueId, int linkIndex, int userD
 	m_data->m_physicsClient->getUserDataInfo(bodyUniqueId, linkIndex, userDataIndex, keyOut, userDataIdOut);
 }
 
+void PhysicsLoopBack::pushProfileTiming(const char* timingName)
+{
+	m_data->m_physicsClient->pushProfileTiming(timingName);
+}
+void PhysicsLoopBack::popProfileTiming()
+{
+	m_data->m_physicsClient->popProfileTiming();
+}