Here's the latest version of my changes to make page tables
relocatable.  Currently they work, but they have not been adequately
tested.  They are also incomplete because top level page tables cannot
be relocated because they cannot be forced to reload across all cpus.
lmbench shows the overhead of rewalking the page tables is less than
that of spinlock debugging.  I'll do real bench marks once everything
is complete.  I wanted to send this out now since I'll be on vacation
and I wanted people to have a chance to look at them sooner rather
than later.

    Ross