Patch from Rik van Riel <riel@imladris.surriel.com>

If a process cannot exit because it's stuck in eg.  a driver, it doesn't make
sense to have the OOM killer kill it repeatedly; that could lead to a hung
system.

Instead, kill another process if the first process we tried to kill hasn't
made any move to exit within 5 seconds.  This way we have a much better
chance of recovering the system.