[PATCH] protocol: Add wl_shell_surface_set_notification

[Bill Spitzak]

I hope and pray this is not just "keep this surface on top" but instead 
an indication that the compositor should actually move it to some 
"notification area".

You do not need "window classes" to keep windows on top. Please don't do 
this as it is detrimental to getting proper floating window support by 
encouraging some idiot to implement "click always raises the window".

Quentin Glidic wrote:
> Notification surfaces are special surfaces that the user should
> always be able to see. The compositor is in charge of displaying
> them to be visible without disturbing the user workflow.