A few updates for x86-64 in 2.5.44. Some of the bugs fixed were serious.

- Don't count ACPI mappings in end_pfn. This shrinks mem_map a lot
  on many setups.
- Fix mem= option. Remove custom mapping support.
- Revert per_cpu implementation to the generic version. The optimized one
  that used %gs directly triggered too many toolkit problems and was an
  constant source of bugs.
- Make sure pgd_offset_k works correctly for vmalloc mappings. This makes
  modules work again properly.
- Export pci dma symbols
- Export other symbols to make more modules work
- Don't drop physical address bits >32bit on iommu free.
- Add more prototypes to fix warnings
- Resync pci subsystem with i386
- Fix pci dma kernel option parsing.
- Do PCI peer bus scanning after ACPI in case it missed some busses
  (that's a workaround - 2.5 ACPI seems to have some problems here that
  I need to investigate more closely)
- Remove the .eh_frame on linking. This saves several hundred KB in the
  bzImage
- Fix MTRR initialization. It works properly now on SMP again.
- Fix kernel option parsing, it was broken by section name changes in
  init.h
- A few other cleanups and fixes.
- Fix nonatomic warning in ioport.c