message: Fix compilation (PHP-7.1 compatibility)
diff: @@ -857,7 +857,7 @@ static PHP_METHOD(swoole_http_response, sendfile)
  zval *zheader = sw_zend_read_and_convert_property_array(swoole_http_response_ce, ctx->response.zobject, ZEND_STRL("header"), 0);
  if (!zend_hash_str_exists(Z_ARRVAL_P(zheader), ZEND_STRL("Content-Type")))
  {
  - add_assoc_string(zheader, "Content-Type", swoole_mime_type_get(file));
  + add_assoc_string(zheader, "Content-Type", (char *) swoole_mime_type_get(file));
  }
  http_build_header(ctx, http_buffer, length);
  