Add vQueueDelete() to the MPU port.

Add vQueueDelete() to the MPU port.
Added volatile key word to the queue xRxLock and xTxLock members.
Ensure the portPRIVILEGED_BIT bit is set when the timer task is being created by the kernel - as it was for the idle task.  Necessary for MPU port.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@1760 1d2547de-c912-0410-9cb9-b8ca96c0e9e2