Add additional asserts to the Keil CM3 and CM4F ports (other CM3/4 ports already updated).
Add the additional yield necessitated by the mutex held count to the case when configUSE_QUEUE_SETS is 0.
Remove some apparently obsolete code from xTaskPriorityDisinherit() (a task cannot be both blocked and giving bac a mutex at the same time].
Update the new "mutex held count" increment and decrement functions to allow mutexes to be created before the scheduler is started.
