Mac build universal binary

[jpcima]

It needs i386 build for compatibility.

[jpcima]

The current dev release is now universal binary, but it's not the whole story unfortunately.

User interface will work only on a host which supports VST2 extension hasCockosViewAsConfig.
https://www.reaper.fm/sdk/vst/vst_ext.php#osx_ext
It's not well documented how much this extension is widespread among the plugin hosts.

By VST2 standard, 64-bit windows are Cocoa, and 32-bit windows are of the deprecated Carbon API from MacOS 9. When the extensions is supported, the plugin is permitted to use Cocoa on 32-bit instead of Carbon.

Plugin framework DPF does not support Carbon, and likely it won't change in the future.

cc @farvardin

[jpcima]

I have had opportunity to test in macOS 32-bit, and found this working in an old Cubase.

I'll take it as fixed for now, and will reconsider if someone requests it.