QTextEngine: text is drawn with wrong font/size when using input method

Change f864bda "Get rid of SpecialData::addFormatIndices" seems to have
broken input method usage (on iOS, at least). If testing with examples/widgets/richtext/textedit example, starting a new pre-edit string, the whole paragraph will be drawn with a much too large font. When the preedit string is committed, it goes back to normal again.

Also, before the change you could go up to the menu and increase the font size. This would increase the font size of the whole word under the cursor immediately. Now the word will instead change once you start writing again.