relay: add "compression" in response to handshake command (weechat protocol)

The value can be "zlib" (default in relay) or "off".

src/plugins/relay/weechat/relay-weechat-protocol.c

@@ -199,6 +199,10 @@ relay_weechat_protocol_handshake_reply (struct t_relay_client *client,
             hashtable,
             "totp",
             (totp_secret && totp_secret[0]) ? "on" : "off");
+        weechat_hashtable_set (
+            hashtable,
+            "compression",
+            relay_weechat_compression_string[RELAY_WEECHAT_DATA(client, compression)]);
 
         msg = relay_weechat_msg_new (id);
         if (msg)

src/plugins/relay/weechat/relay-weechat.h

@@ -60,6 +60,8 @@ struct t_relay_weechat_data
     struct t_hook *hook_timer_nicklist;   /* timer for sending nicklist     */
 };
 
+extern char *relay_weechat_compression_string[];
+
 extern int relay_weechat_compression_search (const char *compression);
 extern void relay_weechat_hook_signals (struct t_relay_client *client);
 extern void relay_weechat_unhook_signals (struct t_relay_client *client);