shell: Introduce workspace manager interface

The workspace manager interface purpose is to provide clients with
control and knowledge about the current workspace state. Initially only
one function and one event exists; moving a surface and state updated
event. A workspace is represented as an index in a 1 dimensional array.

A client keeps track of the state by being broadcasted events when the
state changes, currently limited to current workspace or number of
workspaces available.

A client can send an asynchronous request to the manager asking to move
a surface to workspace identified by an index. It is up to the shell to
actually move it.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>

protocol/Makefile.am

@@ -2,5 +2,6 @@ EXTRA_DIST =					\
 	desktop-shell.xml			\
 	screenshooter.xml			\
 	tablet-shell.xml			\
-	xserver.xml					\
-	text.xml
+	xserver.xml				\
+	text.xml				\
+	workspaces.xml

protocol/workspaces.xml

@@ -0,0 +1,27 @@
+<protocol name="workspaces">
+
+  <interface name="workspace_manager" version="1">
+    <description summary="workspaces manager">
+      An interface for managing surfaces in workspaces.
+    </description>
+
+    <request name="move_surface">
+      <description summary="move surface to workspace">
+	Move the given surface to the specified workspace.
+      </description>
+      <arg name="surface" type="object" interface="wl_surface"/>
+      <arg name="workspace" type="uint"/>
+    </request>
+
+    <event name="state">
+      <description summary="workspace state">
+	The current workspace state, such as current workspace and workspace
+	count, has changed.
+      </description>
+      <arg name="current" type="uint"/>
+      <arg name="count" type="uint"/>
+    </event>
+
+  </interface>
+
+</protocol>