NAME
       SetRast - Set an entire drawing area to a specified color.

   SYNOPSIS
       SetRast( rp, pen )
                a1  d0

        void SetRast( struct rastport *, ubyte );

   FUNCTION
       Set the entire contents of the specified rastport to the
       specified pen.

   INPUTS
       rp - pointer to rastport structure
       pen - the pen number (0-255) to jam into bitmap

   RESULT
       All pixels within the drawing area are set to the
        selected pen number.

   BUGS

   SEE ALSO
        rectfill() graphics/rastport.h