[Libguestfs] RHSrvAny: Fix failure on Windows 2003

The newly rebuilt RHSrvAny worked on Windows XP, Windows 2003 R2, and Windows Vista+, but segfaulted on Windows 2003. After much investigation, the issue seems to have been with inconsistent use of Unicode. This series fixes compilation on Microsoft Visual C++ 2010 (the most recent version which runs on Windows 2003), fixes all compiler warnings, and enabled warnings during the build. The resulting executable now works on Windows 2003 both when built by MSVC 2010 and mingw32 on F19. Matt