[Development] Undeprecating QString::null

[Uwe Rathmann]

On Tue, 16 Jan 2018 17:54:43 +0100, Giuseppe D'Angelo wrote:

> headers of 3rd party libraries
> should be included under -isystem, not -I, to disable warnings in their
> headers.

Yes as there seems to be no BC break ( thanks to all correcting me, I 
should have a deeper look at the code before ) this is a reasonable 
recommendation - at least for platforms, where the option is available - 
I can give my users for now.

Sorry for the noise,
Uwe