Tidy up Win32 port layer - include addition of new variable that prevents recursive...

Tidy up Win32 port layer - include addition of new variable that prevents recursive attempts to obtain a mutex when the trace recorder is used inside an interrupt.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@2713 1d2547de-c912-0410-9cb9-b8ca96c0e9e2