[ticket/11583] Allow FULLTEXT indexes on InnoDB when on MySQL 5.6.4 or higher.

PHPBB3-11583
[ticket/11583] Use a new lang key instead of giving the old one a new meaning.

PHPBB3-11583
Merge remote-tracking branch 'bantu/ticket/11583' into develop-olympus

# By Andreas Fischer
# Via Andreas Fischer
* bantu/ticket/11583:
  [ticket/11583] Use a new lang key instead of giving the old one a new meaning.
  [ticket/11583] Allow FULLTEXT indexes on InnoDB when on MySQL 5.6.4 or higher.