From telepathy-glib in the vicinity of 0.11.15, with g-i git commit c31120dd00d2ea1513399832461ed4437c6940de:

tp_base_client_add_connection_features_varargs: unknown parameter '...' in documentation comment, should be one of 'self', 'feature', None

(and some other similar warnings)

Here's that function's declaration and doc-comment:

void tp_base_client_add_connection_features_varargs (TpBaseClient *self,
    GQuark feature, ...);

/**
 * tp_base_client_add_connection_features_varargs: (skip)
 * @self: a client
 * @feature: the first feature
 * @...: the second and subsequent features, if any, ending with 0
 *
 * The same as tp_base_client_add_connection_features(), but with a more
 * convenient calling convention from C.
 *
 * Since: 0.11.14
 */
void
tp_base_client_add_connection_features_varargs (TpBaseClient *self,
    GQuark feature,
    ...)