Fix \fade corner cases
Fix \fade corner cases

Times in \fade(,,,-1,fadein,fadeout,-1)
are interpreted as in \fad(fadein,fadeout).

Make sure we check the times in the same
order as VSFilter in case they are not sorted.

sanyaade-g2g-repos/libass,torque/libass,stps/libass,pigoz/libass-ct,mwgoldsmith/libass,pigoz/libass-ct,MrSmile/libass,stps/libass,MrSmile/libass,torque/libass,torque/libass,libass/libass,libass/libass,Akemi/libass,sanyaade-g2g-repos/libass,Akemi/libass,grigorig/libass,stps/libass,xbmc/libass,ShiftMediaProject/libass,ShiftMediaProject/libass,mwgoldsmith/libass,sanyaade-g2g-repos/libass,astiob/libass,xbmc/libass,grigorig/libass,astiob/libass,pigoz/libass-ct,mwgoldsmith/libass,Akemi/libass