This is my first step in the migration of page_tables.c to the kernel
types and functions/macros (2.6.23-rc3).  Seems to be working OK.
Signed-off-by: NMatias Zabaljauregui <matias.zabaljauregui@cern.ch>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>