Rewrite PTE manipulation routines to better match the PEM.
Rewrite PTE manipulation routines to better match the PEM.

Document every operation, make sure to call "sync" when appropriate so
that other CPUs see the bit changes and finally grab a lock where it was
missing to grantee atomicity.

ok kettenis@, deraadt@, dlg@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars