First step towards message tags extension support

(see http://ircv3.atheme.org/specification/message-tags-3.2).

In particular this commit implements a (very) dummy implementation
sketch of the server-time extension
(see http://ircv3.atheme.org/specification/message-tags-3.2 and #499).

src/common/proto-irc.h

@@ -17,9 +17,26 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  */
 
+#include <time.h>
+#include "hexchat.h"
+
 #ifndef HEXCHAT_PROTO_H
 #define HEXCHAT_PROTO_H
 
+#define MESSAGE_TAGS_DATA_INIT			\
+	{					\
+		.timestamp=(time_t)0,		\
+	}
+
+/* Message tag information that might be passed along with a server message
+ *
+ * See http://ircv3.atheme.org/specification/capability-negotiation-3.1
+ */
+typedef struct 
+{
+	time_t timestamp;
+} message_tags_data;
+
 void proto_fill_her_up (server *serv);
 
 #endif