process_karaoke_effects: compute \kf from glyph advances, not bounds
process_karaoke_effects: compute \kf from glyph advances, not bounds

Both ways make sense, but traditional VSFilter does it this way.

Akemi/libass,MrSmile/libass,astiob/libass,Akemi/libass,libass/libass,xbmc/libass,MrSmile/libass,libass/libass,astiob/libass,ShiftMediaProject/libass,xbmc/libass,Akemi/libass,ShiftMediaProject/libass