Deprecate i386 for GCC 4.8?

[Steven Bosscher]

Hello,

Linux support for i386 has been removed. Should we do the same for GCC?
The "oldest" ix86 variant that'd be supported would be i486.

The benefit would be a few good cleanups:

* PROCESSOR_I386 / TARGET_386 can be removed

* X86_TUNE_DOUBLE_WITH_ADD can be removed (always true)
* X86_ARCH_CMPXCHG/X86_ARCH_XADD/X86_ARCH_BSWAP can be removed.

* The only ix86 variant without lock-free atomic int support goes
away, which probably allows for a few more cleanups in some of the
libraries (?).

Not much, but something is more than nothing :-)

Ciao!
Steven