Reviewer (Jehan) note: cherry picked from MR !274. Still deciding
whether this will be pushed to gimp-2-10 branch too.
Fixed Conflicts from !274:
app/dialogs/preferences-dialog.c
app/display/gimpdisplayshell-draw.c
app/plug-in/gimppluginmanager-call.c
libgimp/gimp.c
libgimp/gimp.h
libgimpwidgets/gimppreviewarea.c
libgimpwidgets/gimppreviewarea.h
libgimpwidgets/gimpscrolledpreview.c