Converted to true 4levels.  The address space per process is expanded to
47bits now, the supported physical address space is 46bits. 

Lmbench fork/exit numbers are down a few percent because it has to walk
much more pagetables, but some planned future optimizations will
hopefully recover it.

See Documentation/x86_64/mm.txt for more details on the memory map.
Signed-off-by: Andi Kleen <ak@suse.de>

Converted to pud_t by Nick Piggin.
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>