Windows - handle both auto detect proxy settings together

Windows - handle both auto detect proxy settings together

If both "automatically detect settings" and "use automatic configuration
script" are selected in internet options, then respect that.
Because of performance issues, these are tried separately, and
disabled if they fail.

Task-number: QTBUG-13957
Task-number: QTBUG-10238
Change-Id: Ibc824d3039afeaf12c5ea82ed95287e5cf4e1776
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Richard J. Moore <rich@kde.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Shane Kearns <shane.kearns@accenture.com>