proc: add RLIMIT_RTTIME to /proc/<pid>/limits

RLIMIT_RTTIME was introduced to allow the user to set a runtime timeout on
real-time tasks: http://lkml.org/lkml/2007/12/18/218. This patch updates
/proc/<pid>/limits with the new rlimit.

Signed-off-by: Eugene Teo <eugeneteo@kernel.sg>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/base.c

@@ -416,6 +416,7 @@ static const struct limit_names lnames[RLIM_NLIMITS] = {
 	[RLIMIT_MSGQUEUE] = {"Max msgqueue size", "bytes"},
 	[RLIMIT_NICE] = {"Max nice priority", NULL},
 	[RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
+	[RLIMIT_RTTIME] = {"Max realtime timeout", "us"},
 };
 
 /* Display limits for a process */