QGraphicsItem is lacking a way to notify the input method of a changed micro focus

When the micro focus in a widget changes, the input method can be modified by calling QWidget's microFocusChanged() slot.

This mechanism allows for example input methods to correct the placement of input hint windows on the screen as the cursor position changes. Similarly it is also used in the S60 FEP input method to update the text copy in the FEP.

It is not possible for focusable/inputmethod-enabled graphics items to notify the input method about similar changes. Currently the communication is one-way only, from the input method to the item via input method events and inputMethodQuery().

This is needed for https://bugs.webkit.org/show_bug.cgi?id=36292