table

ROW_FORMAT option is lost during CREATE/DROP INDEX.

This fix forces CREATE/DROP INDEX to retain ROW_FORMAT by instructing
mysql_alter_table() that ROW_FORMAT is not used during creating/dropping
indexes.


mysql-test/r/alter_table.result:
  A test case for bug#23404.
mysql-test/t/alter_table.test:
  A test case for bug#23404.
sql/sql_parse.cc:
  CREATE/DROP INDEX must not change ROW_FORMAT. Setting create_info.row_type
  to ROW_TYPE_NOT_USED informs mysql_alter_table that ROW_FORMAT was not
  used during alteration, and thus must be retained.