Miscellaneous fixes from xen-unstable prior to tboot patch set.

Miscellaneous fixes from xen-unstable prior to tboot patch set.

A number of small fixes that were done to address a VT-d fault due
to incorrect memory range checking. Taken from change sets 19061,
19081, and parts of 19083 to 19085.

 On branch master
 Changes to be committed:
	modified:   xen/arch/ia64/xen/mm.c
	modified:   xen/arch/x86/mm.c
	modified:   xen/arch/x86/setup.c
	modified:   xen/arch/x86/tboot.c
	modified:   xen/drivers/passthrough/vtd/iommu.c
	modified:   xen/drivers/video/vga.c
	modified:   xen/include/xen/mm.h