as this is the first opcode TCC supports that has a 0xf3 prefix
and uses integer registers (not SSE ones) this also needs some shuffling
of the prefix code to not generate invalid instructions (the REX prefix
_must_ come directly before the main opcode (including 0f prefix), and
hence needs to come after the 0xf3 prefix). Also disable some mnemonics
in asmtest.S that new GAS doesn't support anymore. The only difference
to GAS (in asmtest.S) is now the 'lock negl' instruction which TCC
emits as 'lock; negl'. That's fine.
2309517066