gdk-pixbuf-io: treat application/gzip like text/plain
gdk-pixbuf-io: treat application/gzip like text/plain

https://bugzilla.gnome.org/show_bug.cgi?id=648815

GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf,Distrotech/gdk-pixbuf,Distrotech/gdk-pixbuf,Distrotech/gdk-pixbuf,GNOME/gdk-pixbuf,Distrotech/gdk-pixbuf,GNOME/gdk-pixbuf,GNOME/gdk-pixbuf