Improvements to GetColumnValue

I've had a chance to merge the changes from 0.6.2 to 0.6.11 into my fork. I'm currently testing it myself.

There are some compatibility changes:
 * ``SQL_TYPE_DATE`` columns are handled (I don't think they were before)
 * Removed _strptime.cpp_ on Windows - it now uses ``mktime`` and ``_mkgmtime32``
 * ``SQL_BINARY`` columns are returned as a node ``Buffer`` object, rather than a hex-encoded string
 * ``SQL_BIT`` columns are handled using the ``SQL_C_BIT`` data type rather than converting to ``SQL_C_CHAR``
 * The ``ODBCResult`` fetch mode can now be ``FETCH_NONE``, which specifies that the columns will be fetched manually
 * ``SQL_VARCHAR`` and ``SQL_BINARY`` columns can be partially requested using the ``maxBytes`` parameter. 

I'd like to implement sending node ``Buffer`` objects for ``SQL_BINARY`` parameters, but I haven't yet had the time.

It's not been thoroughly tested, especially on platforms other than Windows/MSSQL, so there may certainly be issues there. I don't have any other platforms set up, so I can't currently test it on those without a lot of work.