Corrected bug with DropDown-Checked ToolBarItem visualization

Before, the checked state was not visualized with mouse hovering over the dropdown arrow.
Merge branch 'master' of https://github.com/vbRichClient/vbWidgets
Merge pull request #10 from Kbre/master

Bug with DropDown-Checked ToolBarItem visualization

Thanks Kbre, I've merged it.