[CVE-2011-4622] KVM VM triggered host DOS

[Andy Whitcroft]

CVE-2011-4622
	User space may create the PIT and forget about setting up the
	irqchips.  In that case, firing PIT IRQs will crash the host.

The fix for this is currently in the very tip of Linus' tree and should
appear in precise in the next rebase or so.  Note also that KVM does no
exist on ARM so there are no fixes for those branches.  Following this
email are three patches, one for lucid, one for maverick, and one for
natty and oneiric.  These are all simple cherry-picks from the upstream
change, only differing in local context.

Proposing for lucid, maverick, natty and oneiric.

-apw