criu.8: document restore --leave-stopped

Option --leave-stopped can now be used during restore,
but this was not reflected in the man page.

[v2: fix wording]

https://github.com/xemul/criu/issues/215

travis-ci: success for criu.8: document restore --leave-stopped (rev2)
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

Documentation/criu.txt

@@ -284,6 +284,10 @@ Restores previously checkpointed processes.
 *-d*, *--restore-detached*::
     Detach *criu* itself once restore is complete.
 
+*-s*, *--leave-stopped*::
+    Leave tasks in stopped state after restore (rather than resuming
+    their execution).
+
 *-S*, *--restore-sibling*::
     Restore root task as a sibling (makes sense only with
     *--restore-detached*).