Changing the default 32-bit x86 arch for Fedora 12 (#2)

[Bill Nottingham]

Given the loud feedback, I've updated the proposal at:
	https://fedoraproject.org/wiki/Features/F12X86Support

The revised proposal:

- Build all packages for i686 (this requires cmov)
- Optimize for Atom

Why?

- We don't really support i586 in any meaningful matter
- OLPC still works with base i686
- We are likely doing a mass rebuild for F-12 anyways, might as well switch
  while we're doing it
- Atom is the only currently produced 32-bit x86 chip of note; optimize
  for what's currently available

If you want numbers, I did some benchmarking of code [1] with various
build options on a variety of processors, with the F-11 gcc code. All
of these results are relative to a F-11 baseline of "-march=i586
-mtune=generic".

		P4 2.4Ghz	Athlon 3400+	Core2Duo E6850	Atom N270
march=i686/	-1.1%		+2.0%		+0.9%		+0.6%
 mtune=generic
march=i586/	+0.3%		-0.3%		-0.2%		+1.3%
 mtune=atom
march=i686/	-1.5%		+1.2%		+0.5%		+1.7%
 mtune=atom

Bill

[1] gzip, bzip2, math simulation, mp3 encode/decode, ogg encode/decode