PGDump: dataset creation should fail if the filename is invalid

git-svn-id: https://svn.osgeo.org/gdal/trunk@27883 f0d54148-0727-0410-94bb-9a71ac55c965
GTM: declare OLCCreateField and OLCSequentialWrite capabilities

git-svn-id: https://svn.osgeo.org/gdal/trunk@27884 f0d54148-0727-0410-94bb-9a71ac55c965