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/config/accounts.c

@@ -61,10 +61,22 @@ static Autocomplete enabled_ac;
 
 static void _save_accounts(void);
 
+static void
+_accounts_close(void)
+{
+    autocomplete_free(all_ac);
+    autocomplete_free(enabled_ac);
+    free_keyfile(&accounts_prof_keyfile);
+    accounts = NULL;
+}
+
 void
 accounts_load(void)
 {
     log_info("Loading accounts");
+
+    prof_add_shutdown_routine(_accounts_close);
+
     all_ac = autocomplete_new();
     enabled_ac = autocomplete_new();
     load_data_keyfile(&accounts_prof_keyfile, FILE_ACCOUNTS);
@@ -82,15 +94,6 @@ accounts_load(void)
     }
 }
 
-void
-accounts_close(void)
-{
-    autocomplete_free(all_ac);
-    autocomplete_free(enabled_ac);
-    free_keyfile(&accounts_prof_keyfile);
-    accounts = NULL;
-}
-
 char*
 accounts_find_enabled(const char* const prefix, gboolean previous, void* context)
 {