class MessageBuilder

This is a helper build macro for easy building classes with typed message constants.

For example we can define a class like this:

@:build(defold.support.MessageBuilder.build())
class MyMessages {
    var restart_game; // message with no params
    var set_counter:{counter:Int}; // message with params
}

It will be modified by this macro to this:

class MyMessages {
    public static var restart_game(default,never) = new Message<Void>("restart_game");
    public static var set_counter(default,never) = new Message<{counter:Int}>("set_counter");
}

This is handy for defining message enumerations that can later be used by pattern matching in Script.on_message methods.