plugins: Rework UIUGens for Mac

UIUGens used deprecated functions. Fix this and move code to a separate file to indicate obj-c++ compilation

Signed-off-by: Scott Wilson <i@scottwilson.ca>
common: Reimplement sc_ResolveIfAlias in order to avoid deprecation error on Mac

This fixes Issue #875

Signed-off-by: Scott Wilson <i@scottwilson.ca>