conn: implemented xmpp_connect_raw()

This function is similar to xmpp_connect_client(), but doesn't perform
authentication. Instead, it calls user's connection handler immediately
after establishing the connection. Hence, user can implement own
authendication or registration procedures.

Such a "raw" connection can be useful when user interaction is required
(e.g. Data Forms in XEP-0077, OAuth2).

src/auth.c

@@ -288,6 +288,7 @@ static int _handle_proceedtls_default(xmpp_conn_t * const conn,
         xmpp_debug(conn->ctx, "xmpp", "proceeding with TLS");
 
         if (conn_tls_start(conn) == 0) {
+            conn_prepare_reset(conn, auth_handle_open);
             conn_open_stream(conn);
         } else {
             /* failed tls spoils the connection, so disconnect */
@@ -1235,3 +1236,16 @@ int _handle_missing_handshake(xmpp_conn_t * const conn, void * const userdata)
     xmpp_disconnect(conn);
     return 0;
 }
+
+void auth_handle_open_raw(xmpp_conn_t * const conn)
+{
+    handler_reset_timed(conn, 0);
+    /* user handlers are not called before authentication is completed. */
+    conn->authenticated = 1;
+    conn->conn_handler(conn, XMPP_CONN_CONNECT, 0, NULL, conn->userdata);
+}
+
+void auth_handle_open_stub(xmpp_conn_t * const conn)
+{
+    xmpp_warn(conn->ctx, "auth", "Stub callback is called.");
+}