delete a physical segment
int delphseg(ptfig, ptseg)
Pointer to the figure in which the segment should be deleted
Pointer to the segment to be deleted
delphseg delete the segment pointed to by ptseg in the figure
pointed to by ptfig.
The list consistency is maintainded, and the space freed.
delphseg returns 1 if the segment has been deleted, 0
if no such segment exists in the list.
char *was_existing(ptfig, ptseg)
/* if only one exists, it's this one */
return delphseg(ptfig, ptseg) ? "you just killed it!"
: "wasn't here anyway";