Fix interpreter.py to understand the new event data correctly
    
    Completely rewrite the routine, so that the corner cases known
    before (as reported in Phase 1 report) were fixed too.
    Shift-alt is now understood correctly on Czech keyboard, as
    well as the alt_gr is handled fine, similarly to shift.
    Shift, when just pressed, is handled like a modifier, but when
    accompanied by other characters, it is still considered typing.