Introduce our own shutdown callback mechanism.

Instead of adding stuff to `_shutdown()`, we can now register a shutdown
routine from the respective `init()` function of our modules.

This also has the advantage, that we're sure they're called in reverse
order from how the initialization happened.

I didn't simply use `atexit()` because POSIX says that the number of
possible callbacks is limited (min 32) and I was not sure whether
we will maybe extend this number at one point.

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

src/otr/otr.c

@@ -166,12 +166,24 @@ otr_start_query(void)
     return otrlib_start_query();
 }
 
+static void
+_otr_shutdown(void)
+{
+    if (jid) {
+        free(jid);
+        jid = NULL;
+    }
+    otrlib_shutdown();
+}
+
 void
 otr_init(void)
 {
     log_info("Initialising OTR");
     OTRL_INIT;
 
+    prof_add_shutdown_routine(_otr_shutdown);
+
     jid = NULL;
 
     ops.policy = cb_policy;
@@ -187,16 +199,6 @@ otr_init(void)
     data_loaded = FALSE;
 }
 
-void
-otr_shutdown(void)
-{
-    if (jid) {
-        free(jid);
-        jid = NULL;
-    }
-    otrlib_shutdown();
-}
-
 void
 otr_poll(void)
 {