Remove QtWidgets dependencies from QtMacExtras.

This makes it possible to use QtMacExtras from other
modules without adding a QtWidgets dependency. It
also makes it possible to use QtMacExtras from
QtWidgets.

Widget-related classes and functions will be added
to QtWidgets.

Specifics:

Make QMacNativeToolBar private, for use by QMainWindow::
setUnifiedTitleAndToolBarOnMac(). Remove the QAction
based APIs. Remove the example. We can make QMacNativeToolBar
public again when the API is ready and documented.

Remove misc functions: toNSMenu, setDockMenu,
isMainWindow.

Make toCfSTring/Url private pending inclusion into
QtCore.

Change-Id: Ic55e78d8ef923149c23884f6589732f7dfb94153
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Bump qtmacextras version to 5.2.0

Change-Id: I6e1f329b2d4bcf6b54a9db078c5f7064224e8480
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Reviewed-by: Jani Heikkinen <jani.heikkinen@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Doc: Create documentation structure for Qt Mac Extras

Create documentation structure for the module
    - Module qdocconf
    - Documentation pages for module index, namespace/classes,
      examples (not much content yet)

Other doc-related changes
    - Enable running 'make docs' on all platforms
    - Move examples under examples/macextras for a clean
      installing to QT_INSTALL_EXAMPLES
    - Ensure documented classes use correct \inmodule and
      \since commands
    - Add \namespace QtMac
    - Other minor fixes

Change-Id: I1376d68fcd7ab324a5d3355f1d15914092900e5b
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Merge branch 'stable' into dev

Change-Id: Ic97db9f545108ff409016916c343ac903a233ffe