version test macro for DTLS_set_link_mtu

closes #479

Change-Id: Ie0546cf77d1532c88ecf94f0476ce505e845a0cc

daemon/dtls.c

@@ -563,7 +563,9 @@ int dtls_connection_init(struct packet_stream *ps, int active, struct dtls_cert
 #if defined(SSL_OP_NO_QUERY_MTU)
 	SSL_CTX_set_options(d->ssl_ctx, SSL_OP_NO_QUERY_MTU);
 	SSL_set_mtu(d->ssl, 1500);
+#if defined(DTLS_set_link_mtu) || defined(DTLS_CTRL_SET_LINK_MTU) || OPENSSL_VERSION_NUMBER >= 0x10100000L
 	DTLS_set_link_mtu(d->ssl, 1500);
+#endif
 #endif
 
 	d->active = active ? -1 : 0;