Add QtWinExtras_stable to Jenkins

Change-Id: I2a8791959f573fdceb272e8400db1ed7f12ddc60
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
QtDeclarative: Mark win64-msvc2012_developer-build_qtnamespace_Windows_8 tests as insigificant

This is a temporary solution to unblock the CI while the issue is being fixed.

Change-Id: I077ab0d7769825dfd82286002cf10abb71bbc44a
Reviewed-by: Lars Knoll <lars.knoll@digia.com>