CP-6958 - Allow 64bit build.
Increase NR_CPUS to allow for better performance testing.
CA-125197 - Use 32bit blkback ABI if guest does not advertise ABI.
Turn MCE log on.

Require to make mcelog work again.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
CA-125706 - Add a workaround for boot on Nehalem EX machine issue.
CA-120950: fix 64-bit build of the preemptible hypercall support
CP-8081: fix 64-bit path properly in hypercall preemption patch
Merge commit '0c7c04721116b543d2a9a59e3eae9ece515ba0aa'