[SHADOW] Make the guest PT walker more complete.

[SHADOW] Make the guest PT walker more complete.

We now check access rights and write back the _PAGE_ACCESSED and
_PAGE_DIRTY bits into the guest entries as we walk the tables.
This makes the shadow fault handler simpler, and the various emulation
paths more correct.

This patch doesn't add checking and write-back to the HAP pagetable walker;
it just fixes up its arguments to match the new shadow one.

Signed-off-by: Tim Deegan <Tim.Deegan@eu.citrix.com>