* One dead, 37 hurt at checkpoint on Beirut-Damascus highway * Security chief passes checkpoint minutes before blast * Bekaa Valley region has been drawn into Syria conflict (Adds Hezbollah reaction, Security official) By Laila Bassam BEIRUT, June 20 (Reuters) - A suicide bomber killed one person and wounded 37 in an attack at a Security checkpoint in Leba**n on Friday that narrowly missed a top Security official who said he had been told Islamist militants wanted to assassinate him. ...