Don't allow -www etc options with DTLS.

The options which emulate a web server don't make sense when doing DTLS.
Exit with an error if an attempt is made to use them.

PR#3453

apps/s_server.c

diff --git a/apps/s_server.c b/apps/s_server.c
index 9d1a1fa..639bb90 100644
--- a/apps/s_server.c
+++ b/apps/s_server.c
@@ -1532,6 +1532,14 @@
 		sv_usage();
 		goto end;
 		}
+#ifndef OPENSSL_NO_DTLS1
+	if (www && socket_type == SOCK_DGRAM)
+		{
+		BIO_printf(bio_err,
+				"Can't use -HTTP, -www or -WWW with DTLS\n");
+		goto end;
+		}
+#endif
 
 	if (unix_path && (socket_type != SOCK_STREAM))
 		{