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.

FreeRTOS/Source/include/semphr.h

@@ -1154,6 +1154,17 @@ typedef QueueHandle_t SemaphoreHandle_t;
  */
 #define xSemaphoreGetMutexHolder( xSemaphore ) xQueueGetMutexHolder( ( xSemaphore ) )
 
+/**
+ * semphr.h
+ * <pre>TaskHandle_t xSemaphoreGetMutexHolderFromISR( SemaphoreHandle_t xMutex );</pre>
+ *
+ * If xMutex is indeed a mutex type semaphore, return the current mutex holder.
+ * If xMutex is not a mutex type semaphore, or the mutex is available (not held
+ * by a task), return NULL.
+ *
+ */
+#define xSemaphoreGetMutexHolderFromISR( xSemaphore ) xQueueGetMutexHolderFromISR( ( xSemaphore ) )
+
 /**
  * semphr.h
  * <pre>UBaseType_t uxSemaphoreGetCount( SemaphoreHandle_t xSemaphore );</pre>