TextField: Also hide placeholderText when text input is composing
TextField: Also hide placeholderText when text input is composing

Change-Id: I33acdb7edfb6f9792e36e0f9472f0de66ce788d5
Reviewed-by: J-P Nurmi <b84a892f57a298bb5dae653b4e188948a84d5549@digia.com>

mizukusak/qtquickcontrols,drgvond/qtquickcontrols,mizukusak/qtquickcontrols,kobolabs/qtquickcontrols,mizukusak/qtquickcontrols,drgvond/qtquickcontrols,kobolabs/qtquickcontrols,drgvond/qtquickcontrols,kobolabs/qtquickcontrols