Fix the crashes reported by Peter; SHOW CREATE does not call external_lock before calling ::info, and consequently the trx struct in prebuilt is obsolete; setting trx->op_info caused erratic memory corruption in mysqldump


sql/ha_innobase.cc:
  Fix the crashes reported by Peter; SHOW CREATE does not call external_lock before calling ::info, and consequently the trx struct in prebuilt is obsolete; setting trx->op_info caused erratic memory corruption in mysqldump