[CentOS-virt] CentOS 6 Xen: XSAs 167-169, update to Xen 4.6

XSA 169 is out, but is low-priority and has a work-around, so I'm going to batch it together with XSAs 167-168 and release a new 4.4.3 package when the embargo is lifted next Wednesday.

This will be the last XSA update for the 4.4.3 packages. Today or tomorrow I will push the Xen 4.6.0 packages to buildlogs for testing; and sometime after the final 4.4.3 packages are released, I will push the Xen 4.6 packages as the main Xen packages.

The Virt SIG is a community project, so anyone wishing to maintain the Xen 4.4. packages going forward is welcome to step up to do so.

-George