sched: emit thread info flags with stack trace

When a thread is oom killed and fails to exit, it's helpful to know which
threads have access to memory reserves if the machine livelocks.  This is
done by testing for the TIF_MEMDIE thread info flag and should be
displayed alongside stack traces to identify tasks that have access to
such reserves but are still stuck allocating pages, for instance.

It would probably be helpful in other cases as well, so all thread info
flags are emitted when showing a task.

( v2: fix warning reported by Stephen Rothwell )

[ Impact: extend debug printout info ]

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
LKML-Reference: <alpine.DEB.2.00.0905040136390.15831@chino.kir.corp.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>