[RFA] Prec x86 MMX 3DNow! SSE SSE2 SSE3 SSSE3 SSE4 support

[Michael Snyder]

Joel Brobecker wrote:
>>> Let's avoid that extension, as GDB is supposed to be buildable with
>>> a non-GCC compiler.
>> I thought we had given up that requirement?
> 
> You might be right, but I don't remember us making that decision.
> Anyone remembers?

Nah, I'm probably confusing it for when we gave up the
requirement to be compilable by K&R (non-ansii) compilers.