xdg-shell: Drop desktop environment specific state allocations

Instead of allocating state ranges that desktop environments can use as
they want, let them introduce their own protocol and their own enums.

If such desktop environment protocols need the configure/ack_configure
semantics, they can design their protocols to extend xdg_surface, and
make their private configure events a latched state tied to
xdg_surface.configure.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Acked-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Acked-by: Bryce Harrington <bryce@osg.samsung.com>

unstable/xdg-shell/xdg-shell-unstable-v6.xml

@@ -669,18 +669,6 @@
 
 	States set in this way are double-buffered. They will get applied on
 	the next commit.
-
-	Desktop environments may extend this enum by taking up a range of
-	values and documenting the range they chose in this description.
-	They are not required to document the values for the range that they
-	chose. Ideally, any good extensions from a desktop environment should
-	make its way into standardization into this enum.
-
-	The current reserved ranges are:
-
-	0x0000 - 0x0FFF: xdg-shell core values, documented below.
-	0x1000 - 0x1FFF: GNOME
-	0x2000 - 0x2FFF: EFL
       </description>
       <entry name="maximized" value="1" summary="the surface is maximized">
 	<description summary="the surface is maximized">