Patch from Martin Bligh.  It should only affect machines using
discontigmem.

"This patch is was originally from Andrea's tree (from SGI??), and has
been tweaked since by both Christoph (who cleaned up all the code),
and myself (who just hit it until it worked).

It removes _alloc_pages, and adds all nodes to the zonelists
directly, which also changes the fallback zone order to something more
sensible ...  instead of: "foreach (node) { foreach (zone) }" we now
do something more like "foreach (zone_type) { foreach (node) }"

Christoph has a more recent version that's fancier and does a couple
more cleanups, but it seems to have a bug in it that I can't track
down easily, so I propose we do the simple thing for now, and take the
rest of the cleanups when it works ...  it seems to build nicely on
top of this seperately to me.

Tested on 16-way NUMA-Q with discontigmem + NUMA support."