scanner: add defines for wayland interface versions

Currently, it is cumbersome for clients that want to know what version of an
interface is supported at compile time. This can especially matter in cases
where the compositor and client aren't neccesarily compiled against the same
wayland and wayland protocol versions. Provide more information by adding a
simple int define for all interfaces that give the version that is already
defined in the source xml file.

Signed-off-by: Dudemanguy <random342@airmail.cc>

tests/data/empty-server.h

@@ -45,6 +45,11 @@ struct empty_interface {
 		      struct wl_resource *resource);
 };
 
+/**
+ * @ingroup iface_empty
+ */
+#define EMPTY_MAX_VERSION 1
+
 
 /**
  * @ingroup iface_empty