OX: Announce public key on PEP

src/pgp/gpg.c:p_ox_gpg_readkey

Used to read a public key from a file. The function will return the fingerprint
of the file and the base64 encoded key.

src/xmpp/ox.[hc]

ox_announce_public_key(const char* const filename) can be called from the /ox
announce <filename> command. The key within the file will be pushed on PEP and
the Metadata node will be set.

Issue: #1331

src/xmpp/ox.h

@@ -0,0 +1,61 @@
+/*
+ * ox.h
+ * vim: expandtab:ts=4:sts=4:sw=4
+ *
+ * Copyright (C) 2020 Stefan Kropp <stefan@debxwoody.de> 
+ *
+ * This file is part of Profanity.
+ *
+ * Profanity 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.
+ *
+ * Profanity 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 Profanity.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * In addition, as a special exception, the copyright holders give permission to
+ * link the code of portions of this program with the OpenSSL library under
+ * certain conditions as described in each individual source file, and
+ * distribute linked combinations including the two.
+ *
+ * You must obey the GNU General Public License in all respects for all of the
+ * code used other than OpenSSL. If you modify file(s) with this exception, you
+ * may extend this exception to your version of the file(s), but you are not
+ * obligated to do so. If you do not wish to do so, delete this exception
+ * statement from your version. If you delete this exception statement from all
+ * source files in the program, then also delete it here.
+ *
+ */
+
+/*!
+ * \page OX OX Implementation
+ * 
+ * \section OX XEP-0373: OpenPGP for XMPP
+ * XEP-0373: OpenPGP for XMPP (OX) is the implementation of OpenPGP for XMPP
+ * replace the XEP-0027.  
+ *
+ * https://xmpp.org/extensions/xep-0373.html
+ */
+
+
+/*!
+ * \brief Announcing OpenPGP public key from file to PEP.
+ *
+ * Reads the public key from the given file. Checks the key-information and
+ * pushes the key on PEP.
+ *  
+ * https://xmpp.org/extensions/xep-0373.html#announcing-pubkey
+ *
+ * \param filename name of the file with the public key 
+ * \return TRUE: success; FALSE: failed
+ */
+
+gboolean ox_announce_public_key(const char* const filename);
+
+