Function: newsticker-start

Start the newsticker.
Start the timers for display and retrieval. If the newsticker, i.e. the
timers, are running already a warning message is printed unless
DO-NOT-COMPLAIN-IF-RUNNING is not nil.
Run `newsticker-start-hook' if newsticker was not running already.

(fn &optional DO-NOT-COMPLAIN-IF-RUNNING)