implement toxdns3 username lookups

src/dns.h

@@ -0,0 +1,25 @@
+/*  dns.c
+ *
+ *
+ *  Copyright (C) 2014 Toxic All Rights Reserved.
+ *
+ *  This file is part of Toxic.
+ *
+ *  Toxic is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Toxic is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with Toxic.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/* Does DNS lookup for addr and puts resulting tox id in id_bin.
+   Return 0 on success, -1 on failure. */
+int dns3_lookup(ToxWindow *self, uint8_t *id_bin, uint8_t *name, uint16_t id_len);