Base/ToolButtonStyle: fix the background of checked buttons

Task-number: QTBUG-32542
Change-Id: Idcad5f016830f63dae46167ab8a8cd979234a3b2
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
Base/ToolButtonStyle: fix panel's implicit size for textual buttons

Change-Id: Id94be2cf585750c6004d78c0e1b808f30a281bb2
Reviewed-by: Caroline Chao <caroline.chao@digia.com>