Simply some of the alignment calculations in heap_4.c to match those used in heap_5.c.

Simply some of the alignment calculations in heap_4.c to match those used in heap_5.c.
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.