[PATCH wayland] server: Make serial number 0 mean invalid

[Bill Spitzak]

On 10/13/2015 10:28 AM, Jasper St. Pierre wrote:
> In one case, an invalid serial dictates that the window should have it's
> focus attempts prevented. In the no-serial case, focus world be stolen.

Yes, I have heard that. However I still find it hard to believe any 
compositor is going to be implemented that way.

No real compositor is going to allow focus-stealing without a valid 
event. And "toy" compositors will probably allow it for lots of events.