Ensure data cannot be sent to a TCP socket if the socket is in the process of closing.

Ensure data cannot be sent to a TCP socket if the socket is in the process of closing.
Correct definition of StaticTask_t in the case that portUSE_MPU_WRAPPERS is set to 1.
prvTaskCheckFreeStackSpace() now returns configSTACK_DEPTH_TYPE to allow return values greater than max uint16_t value if required.
xStreamBufferSend() and xStreamBufferReceive() no longer clear task notification bits - clearing was unnecessary as only the task notification state is used.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2527 1d2547de-c912-0410-9cb9-b8ca96c0e9e2