An old hack skips use of memory regions < 1MB size, because some machines

An old hack skips use of memory regions < 1MB size, because some machines
put BIOS objects into there, and rely upon them.  We are shocked, SHOCKED,
to find a machine that does so in a large object (Supermicro 5019D-FTN4).
So now we need to ignore memory regions < 32MB in size.  If we put this
memory into use, the zerothread will soon clear it, and on this particular
case the machine resets because something in AML or SMI gets unhappy.
Other machines with similar problems may exhibit other misbehaviours, so
this could fix heisenbugs.  Sadly I expect products to get worse.
ok kettenis, miod