Changes to core code and port layer:

Changes to core code and port layer:
    + Add configASSERT() into ARM Cortex-M ports to check the number of priority
      bit settings.
    + Clear the 'control' register before starting ARM Cortex-M4F ports in case
      the FPU is used before the scheduler is started.  This just saves a few
      bytes on the main stack as it prevents space being left for a later save
      of FPU registers.
    + Added xSemaphoreGetMutexHolderFromISR().
    + Corrected use of portNVIC_PENDSVSET to portNVIC_PENDSVSET_BIT in MPU ports.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2467 1d2547de-c912-0410-9cb9-b8ca96c0e9e2