FTBFS on mingw (cross compiling)

[FauxFaux]

@mjbmr reports that cross compiling fails:

../windows/cygterm.c: In function 'getRegistry':
../windows/cygterm.c:458: error: 'KEY_WOW64_64KEY' undeclared (first use in this function)

This looks like just an old version of mingw (i586-mingw32msvc-) that doesn't support the (XP-era?) KEY_WOW64_64KEY.

However, I can't reproduce this properly on gcc-mingw-w64 (i686-w64-mingw32-) due to various issues; commits to follow.

[FauxFaux]

As of those two patches, I can build a working binary with:

make \
    VER="-DSNAPSHOT=$(date '+%Y-%m-%d') -DSVN_REV=$(svnversion) -DMODIFIED" \
    TOOLPATH=i686-w64-mingw32- \
    TARGET_ARCH= \
    -f Makefile.cyg \
    putty.exe

gcc-mingw-w64-i686:
  Installed: 4.6.3-13ubuntu1+8
        500 http://.../ubuntu/ saucy/universe amd64 Packages