Simple Mandelbrot plotting program for GEM

- Uses VDI drawing
- plotting can be stopped at any time by pressing a key
- does not attempt to calculate clever colors

The program uses a rather simple, non-optimized algorithm.
Versions are provided for 68030+FPU, and 68000. Both use
double-precision for calculation.

Sources is included. In this, Parameters can be set to
run either fullscreen or in a window, and whether the
fractal is drawn from left-to-right or from top-to-bottom.
