Replace the #define that maps the uxRecursiveCallCount to the pcReadFrom pointer...

Replace the #define that maps the uxRecursiveCallCount to the pcReadFrom pointer with a union - although this is against the coding standard it seemed the best way of ensuring complete adherence to the C standard and allow correct builds with LLVM when the optimiser is on.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@1945 1d2547de-c912-0410-9cb9-b8ca96c0e9e2