Apr. 18—Already leading 3-0, a three-hit, three-run fifth inning gave Oklahoma a comfortable lead in its series opener against BYU on Thursday. The Cougars opened up the bottom of the inning with a lead off home run and scored two more runs to keep the pressure on the visiting Sooners. Still, on a night when Oklahoma’s offense had 12 hits and starting pitcher Braden Davis was keeping the Cougars…