These packages make use of gtk3 useflag which indicates that there are issues of migration to gtk+:3.
Gtk3 and similar useflags should be avoided.
Adding to tracker. Please have a look.
Same care as libcanberra. This package provides libraries that are used by both gtk enabled libs + tools (gvnc-1.0, gtk-vnc-1.0 and gtk-vnc-2.0). This is really impractical to maintain if we are to split this package so it'll stay as is for now. Closing wontfix.