Emit selectionChanged signals when input method alters the selection.

Emit selectionChanged signals when input method alters the selection.

Check if the input method removes the selection and force emit
selectionChanged if it sets a new selection.

Task-number: QTBUG-19727
Reviewed-by: Martin Jones
Change-Id: Ic8ea1044d0917aac4e52368f431ac9e5c7db7c56
Reviewed-on: http://codereview.qt.nokia.com/2076
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Andrew den Exter <andrew.den-exter@nokia.com>