NAME
        WaitBOVP -- wait till vertical beam reached bottom of
                    this viewport.

   SYNOPSIS
        WaitBOVP( vp )
                  a0

        void WaitBOVP( struct viewport * );

   FUNCTION
        Returns when the vertical beam has reached the bottom of this viewport

   INPUTS
        vp - pointer to viewport structure

   RESULT
        This function will return sometime after the beam gets beyond
        the bottom of the viewport.  Depending on the multitasking load
        of the system, the actual beam position may be different than
        what would be expected in a lightly loaded system.

   BUGS
        Horrors! This function currently busy waits waiting for the
        beam to get to the right place.  It should use the copper
        interrupt to trigger and send signals like waittof does.

   SEE ALSO
        waittof() vbeampos()