Reviewed by Martin Robinson.

        [GTK] Google sites do not like WebKitGTK+
        https://bugs.webkit.org/show_bug.cgi?id=39617

        Special-case Google domains, and spoof User-Agent when talking to
        them, to stop being treated as a second-class citizen.

        * WebCoreSupport/FrameLoaderClientGtk.cpp:
        (WebKit::initializeDomainsList):
        (WebKit::isGoogleDomain):
        (WebKit::FrameLoaderClient::userAgent): If enable-site-specific-quirks
        is enabled, send the standard WebKit User-Agent string, disregarding the
        custom one set by the browser for Google domains.
        * webkit/webkitprivate.h:
        * webkit/webkitwebsettings.cpp:
        (webkitPlatform): Fix style, and simplify.
        (webkitOSVersion): Ditto.
        (webkitUserAgent): Add the Version/x.y string Safari has been
        using since Safari 2.2.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@67211 268f45cc-cd09-0410-ab3c-d52691b4dbfc