QML text editors need to expose preedit rectangle information

Meego input method style needs to implement word activation on clicks. I.e. clicking on non-preedit word makes it preedit. In order to have it possible, the extra logic on Qt components needs to know if the click happens on top of preedit or not.

QML text editors need to have preedit rectangle(s) information available, or at least some sort of hit test method.