branches/zip: rec_convert_dtuple_to_rec_comp(): Allow externally stored columns to be up to REC_MAX_INDEX_COL_LEN + BTR_EXTERN_FIELD_REF_SIZE bytes in a debug assertion.  This assertion could fail since r2159 in trx_undo_prev_version_build(), because the undo log records for updates and deletes would contain longer prefixes of externally stored columns.
branches/zip: rec_convert_dtuple_to_rec_comp(): Allow externally stored
columns to be up to REC_MAX_INDEX_COL_LEN + BTR_EXTERN_FIELD_REF_SIZE
bytes in a debug assertion.  This assertion could fail since r2159 in
trx_undo_prev_version_build(), because the undo log records for updates
and deletes would contain longer prefixes of externally stored columns.

The assertion failure was reported by Sunny.

flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,ollie314/server,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,ollie314/server,davidl-zend/zenddbi,ollie314/server,davidl-zend/zenddbi,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,flynn1973/mariadb-aix,slanterns/server,ollie314/server,ollie314/server,flynn1973/mariadb-aix,davidl-zend/zenddbi