fix eternal horizontal bullets

vacuum_gambit.p8

@@ -820,7 +820,7 @@ function bullet_base:move()
  self.x += self.dx
  self.y += self.dy
  if (self.f) self.f -= 1
- if (self.y > 145) or (self.y < -8 * self.height) or (self.f and self.f < 0) then
+ if (self.y > 145) or (self.y < -64) or (self.f and self.f < 0) or (self.x > 256) or (self.x < -128) then
   self:die()
   return true
  end