Fix more warning-addition fallout

I'm normally a big fan of small atomic commits, but I also want to get
things done this afternoon...

Bug: https://bugzilla.gnome.org/show_bug.cgi?id=687441
Reviewed-by: Colin Walters <walters@verbum.org>

tests/child-test.c

@@ -51,7 +51,7 @@ gint alive;
 char *argv0;
 #endif
 
-GPid
+static GPid
 get_a_child (gint ttl)
 {
   GPid pid;
@@ -89,7 +89,7 @@ get_a_child (gint ttl)
 #endif /* G_OS_WIN32 */
 }
 
-gboolean
+static gboolean
 child_watch_callback (GPid pid, gint status, gpointer data)
 {
 #ifdef VERBOSE