As reported by Andy Hochhaus in the pyodbc group, SQL Server fails if you compare a
SQL_LONGVARCHAR parameter with a varchar field. Had been using a hardcoded 255 to determine
when to switch from VARCHAR to LONGVARCHAR. Now uses SQLGetTypeInfo to determine the maximum
varchar and binary widths. This will also help performance for programs that bind a lot of
strings greater than 255 but less than their db's max varchar size.