c/r patchset v18 (rc1)

[Oren Laadan]

Working towards a ckpt-v18, I merged all the patches from ckpt-v17-dev
and several other fixes into a clean patchset.

It's available via branch 'ckpt-v18-rc1' on both linux-cr and user-cr.
It applies on 2.6.31.

On this version, I can checkpoint and restart a screen session running
with a couple of shells !

It has been mildly tested here. It is possible that during the somewhat
manual merge I introduced regressions. Let's give it some testing ...

Oren.

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I apologize for the multiple auto-updates from git ... forgot to
disable it before the mega-push of a new branch :(