By Martyn Herman LONDON, March 5 (Reuters) - Jason Kenny fired a timely warning to those targeting his Olympic crown when he swooped to land sprint gold at the world track championships in front of a partisan home crowd on Saturday. The 27-year-old British rider battled back from losing the opening race of the best-of-three final against Australian flyer Matthew Glaetzer to edge the next two. "Those last two rides were tough," said Kenny who won the individual and team sprints at the same London velodrome in the 2012 Olympics. More...