Dogbone notches are now optional and can be set in the gnuplot file.

- cameo/cameo.c (main): use getopt
- cameo/cameo.c (main, usage, process_path): option -d to enable dog-bone
  notches (they're now disabled by default)
- cameo/path.h (struct path), cameo/path.c (path_new, path_from): added
  attribute "notch" to enable notches for a path
- cameo/gnuplot.c (gnuplot_read, gnuplot_do_write): read and write the
  #%notch hint

cameo/path.h

@@ -24,6 +24,7 @@ struct path {
 	struct point *first, *last;
 	double r_tool;	/* mm */
 	int outside;	/* non-zero to mark path as an outside edge */
+	int notch;	/* non-zero to enable dog-boning for path */
 	struct path *next;
 };