configure: remove some unneeded checks
configure: remove some unneeded checks

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