CP-7017: xen: install xen/gntdev.h and xen/gntalloc.h
CP-7017: Add a grant copy ioctl to the gntdev device
CP-7017: Include correct uio.h for grant copy
CA-120950: Call cond_resched() when in the middle of a privcmd hypercall

Hypercalls from privcmd can take a long time.  The hypercall
continuations allow upcalls while the hypercall is in progress so put
a cond_resched() all in the upcall if the upcall interrupted a task
that issues such a hypercall via the privcmd driver.

The should fix the soft lockups in xenguest that may occur with very
long hypercalls when building, saving or restoring large guests.
CA-125706: fix 64-bit kernel boot failure on Nehalem EX

physflat_acpi_madt_oem_check() on Nehalem EX machines results in
physical flat mode being forced on which does not work in a Xen guest.

As a hack, add a test for xen_domain() so physflat isn't forced on.

An upstreamable solution may be to add a Xen specific APIC driver
instead of trying to fiddle with a hardware driver.
CA-123766: replace "tun-ACCESS_ONCE_numqueues.patch" with upstream backport