This destroys the xdg popups associated with a layer surface when the
layer surface is unmapped. It does not make sense to keep the popups
open when unmapped.
The documentation for wayland-server.h says:
> Use of this header file is discouraged. Prefer including
> wayland-server-core.h instead, which does not include the server protocol
> header and as such only defines the library PI, excluding the deprecated API
> below.
Replacing wayland-server.h with wayland-server-core.h allows us to drop the
WL_HIDE_DEPRECATED declaration.
Brian Ashworth
Simon Ser
Guido Günther