Build and test failures with Qt 5.6 and Qt 5.3

[Ivan Čukić]

>> For how long are we going to support [Qt] 5.3?
>
> Good question.
>
> So that we don't need to reopen this discussion regularly, I would like to
> suggest a general rule/policy:
>
> We will always support the last 3 Qt x.y releases.
>
> Right now that means 5.3 + 5.4 + 5.5.
>
> When 5.6 is out, we can drop 5.3.

That sounds ok.

Cheers,
Ivan