1.2 don't let gcc(1) hide warnings in system headers.
Don't disable warning suppression unconditionally, but rather
make in dependent on warn_system_headers flag, one should be
able to use -Wno-system-headers flag if warnings from system
headers are not desired.
non-i386, non-unix, and generatable files have been trimmed, but can easily
be added in later if needed.
gcc-2.7.2.1 will follow shortly, it's a very small delta to this and it's
handy to have both available for reference for such little cost.
The freebsd-specific changes will then be committed, and once the dust has
settled, the bmakefiles will be committed to use this code.
