Audit unlink(1)

One small thing, use argv0 in usage.
Also, add a blank line in link.c which I forgot earlier.

link.c

@@ -19,6 +19,7 @@ main(int argc, char *argv[])
 
 	if (argc != 2)
 		usage();
+
 	if (link(argv[0], argv[1]) < 0)
 		eprintf("link:");