Log Message:
Update xen*46 to 4.6.6, including fixes up to XSA244.
changes since Xen 4.6.5: mostly bug fixes, including security fixes
for XSA206, XSA211 to XSA244.
PKGREVISION set to 1 to account for the fact that it's not a stock Xen 4.6.6.

Note that, unlike upstream, pv-linear-pt defaults to true, so that
NetBSD PV guests (including dom0) will continue to boot without changes
to boot.cfg