Turn Active-DVI portable graphics into scalable graphics:
- all the moveto, rmoveto, lineto, rlineto, curveto, etc, and font_size
commands are proportional to the graphics size (that is x and y are
respectively intyrenally stored as a percentage of size_x, size_y).
- a proportional/absolute flag should also be given that defaults to
proportional (call it scalable as in set_scalable true/false ?).
