NAME
       GetBPen -- Get the B Pen value for a rastport (v39).


   SYNOPSIS
       pen = GetBPen  ( rp )
        d0               a0

        ULONG GetBPen(struct rastport *)

   FUNCTION
        Return the current value of the B pen for the rastport. This function
        should be used instead of peeking the structure directly, because future
        graphics devices may store it differently, using more bits.

   INPUTS
       rp  =  a pointer to a valid rastport structure.

   BUGS

   NOTES

   SEE ALSO
        setbpen() graphics/gfx.h