[VIRT-263 # ARMv8.1-VHE Virtual Host Extensions ]

Rebased on master. Now trying to remember the incantation that produced a minimum number of insns before the kernel actually tries to use this. At present things seem to be crashing before I even get that far, as if I've misconfigured something.

[VIRT-327 # Richard's upstream QEMU work ]

Fixed a couple of bugs in my tcg/ppc host vector patch set.

Reviewed qemu kvm sve patches. Reviewed target/ppc altivec optimization patches. Reviewed GSoC risugen x86 patches. Other misc upstream review.

r~