wayland: generate the wlroots output protocol with any wayland-scanner

The bundled wlr-output-management protocol leaves out the enum
attributes that name another interface's enumeration
(wl_output.transform, zwlr_output_head_v1.adaptive_sync_state).
wayland-scanner resolves such a reference only against the protocol it
is given, so scanners before 1.15 stop with "could not find
enumeration", which failed every build generating the bundled
protocols. The attributes annotate what an argument means and change no
generated C; the arguments keep the types the protocol gives them.

deps/wayland-protocols/wlr/wlr-output-management-unstable-v1.xml

@@ -1,5 +1,13 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <protocol name="wlr_output_management_unstable_v1">
+
+  <!-- The enum attributes qualified with another interface's name
+       (wl_output.transform, zwlr_output_head_v1.adaptive_sync_state)
+       are left out of this copy: wayland-scanner resolves such a
+       reference only against the protocol it is given, so an older
+       scanner fails on them. They annotate an argument's meaning and
+       no generated C differs without them; the arguments keep the
+       types the protocol gives them. -->
   <copyright>
     Copyright © 2019 Purism SPC
 
@@ -243,7 +251,7 @@
         This event describes the transformation currently applied to the head.
         It is only sent if the output is enabled.
       </description>
-      <arg name="transform" type="int" enum="wl_output.transform"/>
+      <arg name="transform" type="int"/>
     </event>
 
     <event name="scale">
@@ -588,7 +596,7 @@
       <description summary="set the transform">
         This request sets the head's transform.
       </description>
-      <arg name="transform" type="int" enum="wl_output.transform"/>
+      <arg name="transform" type="int"/>
     </request>
 
     <request name="set_scale">
@@ -605,7 +613,7 @@
         This request enables/disables adaptive sync. Adaptive sync is also
         known as Variable Refresh Rate or VRR.
       </description>
-      <arg name="state" type="uint" enum="zwlr_output_head_v1.adaptive_sync_state"/>
+      <arg name="state" type="uint"/>
     </request>
   </interface>
 </protocol>