nc: use symbolic SHUT_WR instead of literal 1

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/nc.c b/networking/nc.c
index 126bec9..2f9e174 100644
--- a/networking/nc.c
+++ b/networking/nc.c
@@ -261,7 +261,7 @@
 					if (nread < 1) {
 						/* Close outgoing half-connection so they get EOF,
 						 * but leave incoming alone so we can see response */
-						shutdown(cfd, 1);
+						shutdown(cfd, SHUT_WR);
 						FD_CLR(STDIN_FILENO, &readfds);
 					}
 					ofd = cfd;