Pentium4 branch hints

[Doug Evans]

Alan Modra writes:
 > Inspired by Jan Hubicka's recent patches to teach gcc about Pentium4
 > branch hints, I decided to teach gas about them too.  Allows a line
 > like:
 > 
 >         cs je dest
 > 
 > Of course, you can still do this sort of thing by
 > 
 >         cs
 >         je dest
 > 
 > but if multiple prefixes are involved, it's better to give them to gas
 > on one line.  gas will make sure they are emitted in the proper order.

While using `cs' is ok implementation-wise, at the assembly level ... blech.
There's no mnemonic for remembering which is which.

Don't suppose you want to also accept something like "taken", "not-taken",
as well (or some abbreviation thereof), and have those printed
for disassembly, do you?