Fix some compiler warnings

Void function should actually be declared void. Not-reached switch
condition should still return something.

obt/prop.c

@@ -314,6 +314,7 @@ static gboolean get_text_property(Window win, Atom prop,
         return tprop->encoding == OBT_PROP_ATOM(UTF8_STRING);
     default:
         g_assert_not_reached();
+        return FALSE;
     }
 }
 

openbox/actions/if.c

@@ -46,7 +46,7 @@ void action_if_startup(void)
     actions_register("If", setup_func, free_func, run_func);
 }
 
-static inline set_bool(xmlNodePtr node,
+static inline void set_bool(xmlNodePtr node,
                             const char *name,
                             gboolean *on,
                             gboolean *off)