Fix the dev branch (5.12)

As of 6/2018, various issues block the dev branch:

Windows

Clang fails to parse after "QRegularExpression: refactor pattern optimization" qtbase/06af9a1e3891751d89a64e9013e204176c28ebdc https://codereview.qt-project.org/#/c/232893/ introduced Q_DECL_ENUMERATOR_DEPRECATED_X . This is apparently since we use language level -std=c+1z for MSVC due to some std lib const expr issue in Clang 4. Using -std=c+14 fixes it. We probably need a cmd line option for shiboken for this anyways..

macOS

• 3D Extras test hangs, "QOpenGLContext::swapBuffers() called with non-exposed window, behavior is undefined"
• Various tests hang/fail QtWidgets::bug_750(), QtWidgets::bug_919() QtWidgets::paint_event_test() QtWidgets::qpen_test(), QtWidgets::qpicture_test(), QtWidgets::qstyle_test() QtWidgets::virtual_pure_override_test(), QtQml::bug_825()
  QtQml::bug_847()