csd: Improve csd decorations
csd: Improve csd decorations

Only treat buttons with the titlebutton class as window buttons,
and try to rtl right by looking for left/right boxes. These were
just added in gtk.

Distrotech/gnome-themes-standard,rgcjonas/adwaita-semidark,DoctorJellyface/gnome-themes-standard,rgcjonas/adwaita-semidark,rgcjonas/adwaita-semidark,DoctorJellyface/gnome-themes-standard,Distrotech/gnome-themes-standard,rgcjonas/adwaita-semidark