rename keycode, mousecode enumerations

src/data/setting.hpp

@@ -42,13 +42,13 @@ public:
         : Setting(format), initial(value), value(value) {
     }
 
-    observer_handler observe(consumer<T> callback, bool callOnStart = false) {
+    ObserverHandler observe(consumer<T> callback, bool callOnStart = false) {
         const int id = nextid++;
         observers.emplace(id, callback);
         if (callOnStart) {
             callback(value);
         }
-        return observer_handler([this, id]() {
+        return ObserverHandler([this, id]() {
             observers.erase(id);
         });
     }