LONDON (Reuters) - World oil prices tumbled from 13-year peaks at $40 Monday after leading world exporter Saudi Arabia said OPEC should raise supply to stop high prices hurting world economic growth. The Saudi remarks reassured markets after a sabotage pipeline attack at the weekend struck Iraq's crude exports, reinforcing fears over Middle East supply security. U.S. light crude slumped $1.30 a barrel to $38.63, after striking the $40 mark Friday for the first time since October 1990 in the run up to the first Gulf War. London's Brent crude was down $1.35 at $35.65 a barrel. Prices slid after...