Update to gcc 4.7 20120224 snapshot and perform a bootstrap build
    
    - Update to gcc 4.7 20120224 snapshot
    - Perform a bootstrap build using mingw-w64
    - Dropped the /lib/i686-pc-mingw32-cpp symlink
    - Dropped the float.h patch as it isn't needed anymore with mingw-w64
    - Added some patches which upstream mingw-w64 recommends us to apply