--catch-up option: Show progress relative to the targeted session

I intentionally ignored this when I added the --catch-up option because I
had the idea it would be messy in several ways, but I came to realize the
code is trivial and bullet proof.  See openwall#4761

src/status.c

@@ -454,6 +454,9 @@ void status_print(void)
 	if (options.flags & FLG_STATUS_CHK)
 		percent_value = status.progress;
 	else
+	if (options.catchup && john_max_cands) {
+		percent_value = 100.0 * status.cands / john_max_cands;
+	} else
 	if (status_get_progress)
 		percent_value = status_get_progress();