[qtmozembed] Handle digits in inputMethodEvent as key events

This is applied only for Qt::ImhFormattedNumbersOnly and Qt::ImhDialableCharactersOnly
hints.

InputMethod is reset once key events have been sent. Virtual
keyboard keys like "*p" of dialable characters are still handled
as a text event.
Merge pull request #60 from rainemak/digitHandling

[qtmozembed] Handle digits in inputMethodEvent as key events