Hi Andrew.

Attached is a new espfix cleanup patch.
- Introduced PER_CPU() macro to be used from asm
- Introduced GET_DESC_BASE() macro to be used from asm
- Rewrote the fixup code in asm, as calling a C code with
the altered %ss appeared to be unsafe
- No longer altering the stack from a .fixup section
- 16bit per-cpu stack is no longer used, instead the 32bit
stack is used, and the base is patched the way so that the
high word of the kernel and user %esp are the same.
- I think that the limit of regs->esp+THREAD_SIZE*2 is very
permissive too (and I don't want to mess with granularity),
so I left the default 4G limit, unless Zach will really
complain on that. :)

Signed-off-by: Stas Sergeev <stsp@aknet.ru>
Acked-by: Zachary Amsden <zach@vmware.com>