Replace setproctitle dummy macro with a function stub

This way we can replace it later on with a real implementation so that
applications can immediately benefit from it w/o the need to recompile
them.

Versions

@@ -58,5 +58,7 @@ LIBBSD_0.2 {
     pidfile_write;
     pidfile_close;
     pidfile_remove;
+
+    setproctitle;
 } LIBBSD_0.1;