There is some redundant code and unnecessary function calls where 
inlines would be more appropriate in many of the sub-arches of i386.  In 
addition, some subarches do not compile with certain kernel config 
options, which needed to be fixed.  I have attempted to clean up the 
subarch implementation of i386 by removing the requirement of 
implementing a complete setup.c; instead, architectures are free to 
define only the hooks they actually need in the subarch headers, by 
introducing mach-xxx/mach_hooks.h and putting the generic definitions in 
arch_hooks.h.

I have tested this as best as I can, and all of the subarches continue 
to compile (in fact, even better with the config fixes).  I don't have 
all of the hardware combinations to actually test the generated kernels, 
but in general, this is fairly straightforward code movement.  One 
liberty I took was removing the sub-arch hook for mca_nmi_handler, as it 
is clear this does not apply to any other subarch than Voyager.

I created a new file, arch/i386/default.c, which has the default 
functions that are appropriate for all kernel compiles, which removes 
the redundant need to redefine IPI mechanisms in all architectures that 
provide a setup.c file.  This was required, since Voyager chooses to 
override the entire functionality of smp.c.

Comments, suggestions, anything welcome.  I think this is a much cleaner 
approach, and both new and existing sub-architectures will benefit.  I 
am sorry this patch is so large, but it is very difficult to separate 
into multiple steps that still allow all the subarches to compile.

Zach