Thisintroduces __GFP_ZERO as an additional gfp_mask element to allow to
request zeroed pages from the page allocator:

 - Modifies the page allocator so that it zeroes memory if __GFP_ZERO is
   set

 - Replace all page zeroing after allocating pages by prior allocations with
   allocations using __GFP_ZERO
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>