MTS-ETP: micro-tuning support for synths.

[p0nce]

It's some additional callbacks for supporting micro-tuning in synths https://github.com/ODDSound/MTS-ESP

Need to implement the callbacks in the client, along with the implementation of said callbacks.

[p0nce]

I don't actually like this... this should be in the plugin formats.

[p0nce]

Could be interesting, as I received a support email quite appreciative of what MTS-ETP can do.