First MAM test

Send a request (which we can't handle yet) :-)

Regards https://github.com/profanity-im/profanity/issues/660

src/xmpp/xmpp.h

@@ -237,6 +237,7 @@ void iq_autoping_check(void);
 void iq_http_upload_request(HTTPUpload *upload);
 void iq_command_list(const char *const target);
 void iq_command_exec(const char *const target, const char *const command);
+void iq_mam_request(ProfChatWin *win);
 
 EntityCapabilities* caps_lookup(const char *const jid);
 void caps_close(void);