Change the "feature not implemented" dialog to a more standard looking MessageDialog
drwxr-xr-x - ETL
drwxr-xr-x - autobuild
drwxr-xr-x - gtkmm-osx
drwxr-xr-x - synfig-core
drwxr-xr-x - synfig-osx
drwxr-xr-x - synfig-studio