Odbc driver: clear fields before fetching
Odbc driver: clear fields before fetching

Fix submitted by Warwick Smith in [1].

Ensures the fetched recordset does not contain any data left over from
an earlier fetch operation.

[1] http://phplens.com/lens/lensforum/msgs.php?id=17539

paulproteus/ADOdb,paulproteus/ADOdb,andrewnicols/ADOdb,ipso/ADOdb,pyscht/ADOdb,pyscht/ADOdb,andrewnicols/ADOdb,azghanvi/ADOdb,ipso/ADOdb,azghanvi/ADOdb