An effort has been made to support more keyboard layouts that provide
dead keys (US international, Mac-specific dead keys).
The dead key is translated now at the event conversion phase, not
when it is actually used for modifying keys, which simplifies the logic.
Unittests have been created to check the translation mechanism.
Fixes: QTBUG-86272
Change-Id: I07f7d63f5a37f8469c693b034b400da99379f519
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
