bitkeeper revision 1.1236.34.3 (4237063cE2rat5RdEGCsTzuaC6XCcA)

bitkeeper revision 1.1236.34.3 (4237063cE2rat5RdEGCsTzuaC6XCcA)

Tidy the x86 emulator interface, and use it from within the
writable pagetable algorithm to deal with otherwise unhandleable cases.
For example: L1 mapped at multiple L2 slots; L1 that maps itself; L1
that also maps the code making the update, or the kernel stack.
This provides a proof-of-concept for the emulator that can be picked
up for the VMX code to improve the device-model emulation.
Signed-off-by: Keir Fraser <keir@xensource.com>