Bring DatabaseMetaData feature tests up to date:

* NULLs are sorted differently in 7.2
* table correlation names are supported
* GROUP BY, ORDER BY unrelated is supported since 6.4
* ESCAPE/LIKE only supported since 7.1
* outer joins only since 7.1
* preferred term for procedure is "function"
* preferred term for catalog is "database"
* supports SELECT for UPDATE since 6.5
* supports subqueries
* supports UNION; supports UNION ALL since 7.1
* update some of the max lengths to match reality
* rearrange some functions to match the order in the spec
  for easier maintenance