.. and use YQ2ARCH and YQ2OSTYPE instead of just ARCH and OSTYPE
for the defines, so it's consistent with the engine and xatrix+rogue.
$PROCESSOR_ARCHITECTURE seems to contain the architecture of the host,
but we need the architecture the current MinGW shell is targeting.
$MINGW_CHOST seems to be just that, and on my system it's either
i686-w64-mingw32 (mingw32.exe) or x86_64-w64-mingw32 (mingw64.exe)
(No idea what it looks like for Windows on ARM...)
As fixing this would otherwise break existing savegames, I bumped the
SAVEGAMEVER to "YQ2-4" and added a quirk for older savegameversions:
On Windows i386 savegames that contain "AMD64" instead of "i386" as
architecture are also accepted.
(For YQ2-1 this didn't seem necessary, apparently "i386" was hardcoded)
