VST3 hosting!

I've just committed an initial release of support for VST3 hosting. Would be great if any of you who have hosting apps (and anyone who builds VST3 plugins) could give it a whirl!

Thanks to Joel Langlois for most of the donkey-work on this one! We'll be following up with a VST3 plugin wrapper as soon as possible, but needed to get the hosting side finished first, because it'll be going into Tracktion 5 pretty soon.

As I said, any feedback on problems would be greatly appreciated - in testing, a few plugins just seem to die in bizarre and inexplicable ways, which is mostly impossible to debug from the host side, so it'd be immensely useful to hear from any VST3 plugin devs whose plugins don't work, and who could tell us from the "inside" what it is that's not making their plugins barf.