gcc: add more warning flags.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
gcc: expand on -mieee for alpha.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
gcc: add additional i386/amd64-specific options.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>