OSU DNA combination macros

[EvanKirshenbaum]

@cumbiem has asked for some help with OSU's new DNA combination macros:

This mostly looks straightforward, but it does point out that it would be really useful to be able to be able to have a macro return multiple values. There are a couple of places where the most natural implementation would return two or four drops.

It also points out that optional parameters would be quite useful for things like mixing. Currently, the mix macro takes three parameters: the center pad and the direction to the two drops. Almost always, the other drop will be directly across.

Migrated from internal repository. Originally created by @EvanKirshenbaum on Jun 30, 2023 at 2:28 PM PDT.