LAS VEGAS — It was close for a while, then the Lakers dropped the hammer on the Sacramento Kings in the second quarter of tonight’s exhibition at the Thomas & Mack Center. Andrew Bynum got the Lakers started by scoring 16 of his 20 points in the first quarter. Kobe Bryant added 10 points by halftime. Neither Pau Gasol nor Luke Walton dressed. Gasol has a strained right hamstring and Walton has a sore back. Bynum filled the void created by Gasol’s absence. He torched Sacramento’s Spencer Hawes again and again.