merge changes back upstream
A year ago, upstream expressed skepticism at porting their code to GTK3, in this bug report. Or at least, they said clearly they wouldn't support both GTK2 and GTK3 and said they would prefer supporting GTK2 for now because "gtk2 remains more common on linux distros".
I think it's time to review that assertion: GTK2 is going away on many Linux distribution and GTK3 is certainly shipped everywhere. Therefore, the changes here should be proposed back upstream to resolve this fork.
This is blocking Debian packaging: we don't want to package an ephemeral fork and would prefer to stick with the official package, unless this because the official "dialog" go client that everyone uses.