Added tests2/test.py
Use SQL_DATA_AT_EXEC instead of SQL_DATA_LEN_AT_EXEC when possible.

Some drivers have problems with the LEN version, so eliminating use when possible.

There is an ODBC GetInfo query to determine if LEN is required.  Upon connection, this is
cached and LEN is used if this is 'y'.  FreeTDS, for example, requires LEN in some cases.
Added support for pickling Row objects.