David Beckham is retiring from soccer, ending a career in which he became a global superstar who transcended the sport.   The 38-year-old, who recently won a league title in a fourth country with Paris Saint-Germain said this morning that he will retire at the end of this season.  Beckham, whose forays into fashion and marriage to a pop-star wife have made him an international celebrity, has two more patches left at PSG.  He has been giving his salary to a children's charity.  "I want to thank all my teammates, the great managers that I had the pleasure of learning from,"  Beckham said.   "I also want to thak the fans who have all supported me and given me the strength to succeed."