Cynthia Littleton Business EditorWhen Drew Barrymore started on the path to becoming a daytime talk-show host, her industry pals were quick to warn her that the daily grind of hosting a syndicated talker is one of the most demanding jobs in showbiz.That was more than a year ago. The work has only gotten more complicated since then.“It’s a giant undertaking,” Barrymore tells Variety while on a break from shooting content for the CBS-distributed “The Drew Barrymore Show,” which debuts Sept.