More DRY in configure/versionator
MingW cross compiling on Mac

Works a treat. Provided you install the binaries from here: http://crossgcc.rts-software.org/doku.php?id=compiling_for_win32 I have contacted the guy for his Formula for Homebrew usage as I couldn't compile the cross compiler myself. Didn't work.
We are now building with MingW64

MingW64 is way more maintained. For instance, it provides WinHTTP.h.

Also fixed some versioning issues. Removed installer.rc since it was 80% the same as rackmate.rc and just added another define when compiling for the installer. DRY'd some more versioning macros and variables in the makefiles.

Some fixes to configure for mingw on Mac.