HOUSTON -- Grammy-winning Tejano singer Emilio Navaira's survival was in doubt Monday after the tour bus that police said he was not licensed to drive crashed on a freeway, leaving him with serious head injuries."There is a chance he may not make it," said Dr. Alex Valadka, director of neurotrauma services at Memorial Hermann-Texas Medical Center and vice chair of neurosciences at the University of Texas Health Science Center at Houston."Everyone needs to understand that right up front. That's how bad it is."Navaira, 45, known to his fans simply as Emilio, was removed from the bus that wrecked before dawn...