Get rid of warnings when compiled with -Wformat-security

Change-Id: Ibe59f9704dc03aa592fce6ca6d422f4d4e6153cb
diff --git a/netcat.c b/netcat.c
index c1d3f08..16a58a5 100644
--- a/netcat.c
+++ b/netcat.c
@@ -198,7 +198,7 @@
       if (h_errno > 4)		/* oh no you don't, either */
 	fprintf (stderr, "preposterous h_errno: %d", h_errno);
       else
-	fprintf (stderr, h_errs[h_errno]);	/* handle it here */
+	fprintf (stderr, "%s", h_errs[h_errno]);	/* handle it here */
       h_errno = 0;				/* and reset for next call */
     }
 #endif