Updated Win32 cross-compilation tools

I’ve updated the Windows cross-compiling tools to the latest version
of gcc and mingw32. You can get them here:
http://www.libsdl.org/extras/win32/cross/README.txt
http://www.libsdl.org/extras/win32/cross/mingw32-linux-x86-glibc-2.3.tar.gz

Enjoy!
-Sam Lantinga, Software Engineer, Blizzard Entertainment