When the surface is closed, we destroy all pending serials waiting to be
accepted. This means we need to ignore any future ack events, because we
can have the following events:
1. -> configure()
2. -> close()
3. <- ack_configure()
At point 3, wlroots will error the client because of invalid serial,
however the client hasn't processed close() yet.
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.
Ilia Bozhinov
Brian Ashworth
Simon Ser
Guido Günther