Track which [Script Info] headers have been set
Track which [Script Info] headers have been set

And warn about duplicate headers

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