Add a USE_64_BIT_INT build option to the Windows makefiles.

Add a USE_64_BIT_INT build option to the Windows makefiles.

Rather than adding more canned configurations, we dynamically set values
which differ from the standard 32-bit build options, and actually remove
the canned configurations for 64-bit builds too and do likewise for them.

The ~ARCHPREFIX~ games used by the outgoing .gc64 configuration needed
bringing into the remaining .gc configuration to maintain support for the
GCCCROSS build option.

Two tweaks to sv.c were required for the USE_64_BIT_INT option to work
with a VC++ build, allowing the I64 printf size specification. The GCC
build worked anyway since it uses ll rather than I64.

The motivation for this change came from a patch submitted by Sisyphus
<sisyphus1@optusnet.com.au>:
Message-ID: <6AC52DD00C96415A9E919A02F12DD05F@desktop2>