Modified InformixPlatform::getPostAlterTableIndexForeignKeySQL().

Passed the instance of the platform as the first argument to
TableDiff::getName() required now by the method.

See https://github.com/doctrine/dbal/commit/312f5d3ead1475f89d6c2e1d53c1651250dbae4c
Fixed errors in nformixPlatform::getAlterTableSQL().

- Fixed wrong order of the SQLs generated when the table is renamed
  with foreign key indexes.
- Fixed table renaming when it needs quoting.
Added new tests to InformixPlatformTest.
Locked new DBAL commit.