[CVE-2011-2699] ipv6: make fragment identifications less predictable

[Andy Whitcroft]

CVE-2011-2699
	Fernando Gont discovered that the IPv6 stack used predictable
	fragment identification numbers. A remote attacker could exploit
	this to exhaust network resources, leading to a denial of service.

Fixes for this have hit Oneiric and P via mainline and stable updates.
Following this email are patches for natty, natty/ti-omap4, maverick,
maverick/ti-omap4, lucid, lucid/fsl-imx51, and hardy.  These are all
relativly minor backports, though there are variations as we roll
backwards.

As there are currently no security tests for these, and because they
ony affect a very tiny fragmentation case they are hard to actually test.
These have only been compile tested.  They have been reviewed by eye and
appear sensible in context.

Proposing for natty, natty/ti-omap4, maverick, maverick/ti-omap4, lucid,
lucid/fsl-imx51, and hardy.

-apw