teach set_special_pids() to use struct pid

Change set_special_pids() to work with struct pid, not pid_t from global name
space. This again speedups and imho cleanups the code, also a preparation for
the next patch.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/sys.c b/kernel/sys.c
index e13bc51..c326d6d 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1065,7 +1065,7 @@
 		goto out;
 
 	group_leader->signal->leader = 1;
-	__set_special_pids(pid_nr(sid), pid_nr(sid));
+	__set_special_pids(sid);
 
 	spin_lock(&group_leader->sighand->siglock);
 	group_leader->signal->tty = NULL;