Have support for making commited words in text entries as preedit in input method side

In Meegotouch text entries we have implemented an input method extension for making words preedit from the widget side. This works so that when user clicks on a word, it will be injected back to input method server as preedit, becomes underlined and can be edited as a whole, i.e. error correction can be applied to the whole word. Similar possibility would be nice to have with standard Qt interfaces.

MeegoTouch implementation in more detail:
1. MTextEdit mouse click handler detects word boundaries around click position
2. MTextEdit removes the word from contents, makes an MPreeditInjectionEvent with the word and sends that to input context.
3. If event was not accepted, it is assumed the input context doesn't support such feature, otherwise input context updates the word to input method server and input continues in preedit mode.