[Xcb] xpyb: ConfigureWindow bug + fix suggestion

[Tad]

I'm playing around with xpyb, and I'm getting BadValue errors when
attempting to use xcb.xproto.ConfigureWindow. It seems that the
padding bits are sent after the value_list, rather than before (as I
believe it should be). I haven't gone into any depth in the generation
code, but the fix I applied was to reverse the order of the following
lines in xproto.py:

        buf.write(str(buffer(array('I', value_list))))
        buf.write(pack('2x', ))

The function then works as expected.