[PATCH] Free discarded sbuf in hook_add()

Note: this is a very insignificant leak due to how rarely addhook would be
called in everyday usage, but it's a leak nonetheless, so I thought I'd mention
it.

hook.c:hook_add() fails to free sbuf containing command (allocated by
actions.c:cmd_addhook()), when that command is already present in the hook,
resulting in a leak every time the user tries to re-add the same command to a
hook.

To reproduce, add a command to a hook twice, for example, by running:
$ ratpoison -c "addhook quit abort"; !#
which results in (taken from valgrind's log):

46 (40 direct, 6 indirect) bytes in 1 blocks are definitely lost in loss record 73 of 200
   at 0x4C2C04B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x41BDCE: xmalloc (main.c:74)
   by 0x41F625: sbuf_new (sbuf.c:30)
   by 0x4106A4: cmd_addhook (actions.c:5218)
   by 0x40A882: command (actions.c:2557)
   by 0x40AA70: cmd_colon (actions.c:2597)
   by 0x40A882: command (actions.c:2557)
   by 0x415B22: handle_key (events.c:423)
   by 0x415BD8: key_press (events.c:459)
   by 0x416663: delegate_event (events.c:840)
   by 0x416AF5: listen_for_events (events.c:1008)
   by 0x41D187: main (main.c:749)

The attached patch fixes the issue. It was generated over the latest git,
v1.4.6-48-gb02d855.

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diff -pdru ratpoison/src/hook.c ratpoison.build/src/hook.c
--- ratpoison/src/hook.c	2013-08-07 12:08:11.161005020 -0300
+++ ratpoison.build/src/hook.c	2013-08-07 13:18:16.804773548 -0300
@@ -34,7 +34,10 @@ hook_add (struct list_head *hook, struct
   list_for_each_entry (cur, hook, node)
     {
       if (!strcmp (sbuf_get (cur), sbuf_get (s)))
-        return;
+        {
+          sbuf_free (s);
+          return;
+        }
     }
 
   /* It's not in the list, so add it. */