This avoids re-creating existing foreign keys with a different name,
after migrating from Hibernate 4 to Hibernate 5 (as implicit naming
convention has changed).
Actually, some RDBMS allow it (PostgreSQL, MySQL, MS SQL Server, ...)
and duplicate the same key, whereas others (Oracle, ...) do not
allow it and Schema update fails.
This fix ignores the case of the table and column name when checking
if a equivalent Foreign Key already exists (whatever its name)
Closes https://hibernate.atlassian.net/browse/HHH-13779
0b819863f2