Allow mouse events when transient scroll bars are hidden

On mac, while transient scroll bars are not visible it was not
possible to interact with the viewport as the mouse events were
consumed by the scroll view.

This makes the ScrollBar mouse area disabled before a scroll is
triggered. Note that I also added a minor workaround to ensure
that we update the mouse cursor.

Task-number: QTBUG-32400
Change-Id: If091edf054fcab65feb9b8c8e5c45e25431f4be4
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
ToolBar: Improved aestetics for Fusion style

We were drawing an ugly double gray line and had uneven spacing
between tool buttons and margins.

Change-Id: Ifd2a30cb2ae8f3fb31b5df8410e17cfbd1175978
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Merge remote-tracking branch 'origin/stable' into dev

Change-Id: I2f557f40e078a91d81e1a4683bf5d3d4a5dc95e8