fcl-db:
* Fixes tests for UniDirectional datasets
* Calculated fields are supported by UniDirectional datasets
* Lookup fields return always null for UniDirectional datasets in Delphi
* First is valid for UniDirectional datasets (in TDataSet.First closes/opens dataset if not at Bof)

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@23307 3ad0048d-3df7-0310-abae-a5850022a9f2