Slider: fix qdoc warnings
Slider: fix qdoc warnings

Change-Id: I85578b85ddad347e84dab71395fa5394d0e5cb8e
Reviewed-by: Caroline Chao <cb6a0059f4e516e853a34cb558c25ca5a9bcf4ab@digia.com>

mizukusak/qtquickcontrols,jfaust/qtquickcontrols,kobolabs/qtquickcontrols,drgvond/qtquickcontrols,kobolabs/qtquickcontrols,mizukusak/qtquickcontrols,kobolabs/qtquickcontrols,richardmg/qtcomponents,jfaust/qtquickcontrols,richardmg/qtcomponents,mizukusak/qtquickcontrols,richardmg/qtcomponents,drgvond/qtquickcontrols,drgvond/qtquickcontrols,jfaust/qtquickcontrols