lexer: clarified `.lastIndex` hack
lexer: clarified `.lastIndex` hack

raine/LiveScript,satyr/coco,cesarmarinhorj/LiveScript,edwin0258/LiveScript,goatslacker/LiveScript,Champii/LiveScript,gkz/LiveScript,gkz/LiveScript,Champii/LiveScript,rhendric/LiveScript,RobLoach/LiveScript,edwin0258/LiveScript,rhendric/LiveScript,RobLoach/LiveScript,raine/LiveScript,cesarmarinhorj/LiveScript