[PATCH] large x86 setup cleanup.

[PATCH] large x86 setup cleanup.

Patrick Mochel did a great job here at splitting up some of the larger
messy parts of arch/i386/kernel/setup.c, and introduced a nice abstraction
which gives us a much nicer way to ensure we can add workarounds for vendor
specific bugs / features without polluting other vendor code paths.

Mark Haverkamp also brought this up to date for merging in my tree circa
2.5.14, and asides from 1-2 now fixed small thinkos, there haven't been
any problems.

This also features a workaround for an errata item on stepping C0 of
the Intel Pentium 4 Xeon, which isn't in your tree yet, where we must
disable the hardware prefetcher to ensure sane operation.