clear_alt_pal_bits to reset what sea setup does

vacation.p8

@@ -513,7 +513,7 @@ end
 
 function title_screen:draw()
  pal()
- memset(0x5f78,0x0,8)
+ clear_alt_pal_bits()
  cls(12)
  print("title screen", 30, 57, 0)
  print("press right arrow", 15, 66, 0)
@@ -818,6 +818,10 @@ function wave(toff)
  return 2.5 * sin((t()+toff)>>1)
 end
 
+function clear_alt_pal_bits()
+ memset(0x5f70,0x0,16)
+end
+
 sea = {}
 mknew(sea)