* If you're in an array, @fieldname must be NULL. If you're in an
* object, @fieldname must be non-NULL. This is checked if
* CCAN_JSON_OUT_DEBUG is defined.
* @fieldname must not need JSON escaping.
*
* If you're in an array, @fieldname must be NULL. If you're in an
* object, @fieldname must be non-NULL. This is checked if
* CCAN_JSON_OUT_DEBUG is defined.
* @fieldname must not need JSON escaping.
*