The following patches change x86_32 to use native format for the boot
time page tables. The first two are taken directly from Eric
Biederman's older patch series
http://marc.info/?l=linux-kernel&m=117794868309910&w=2 and
http://marc.info/?l=linux-kernel&m=117794868819193&w=2 while the final
patch is http://marc.info/?l=linux-kernel&m=117795243926186&w=2
updated for the current tree (much of it was already in, the rest has
been extensively modified).

Changes since v1:
 - Grabbed Eric's patches for enabling PAE in head_32.S -- I think
   they are cleaner than what I had.
 - Use native_* accessors instead of #undef CONFIG_PARAVIRT. This
   approach seem cleaner and also allows the code to live in init_32.c
   instead of creating a new file.
 - Ensure we map enough pages to create a full 4G mapping of
   lowmem. This now includes the space for the initial page tables
   rather than being in addition too.
 - Continue to map extra pages for CONFIG_DEBUG_PAGEALLOC and some
   extra pages for slack, per the original assembly code.

Cheers,
Ian.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Mika Penttilä <mika.penttila@kolumbus.fi>