Fixes to get fedex_plus working in release build on MSVC2010.
- Added __STDC__ define for MSVC builds, seems otherwise an access violation occurs on release builds.
- Added #ifdef YYDEBUG to fix build issue in fedex_plus release build.
Merge pull request #220 from stepcode/dw/msvc_release_fixes

Fixes to get fedex_plus working in release build on MSVC2010.