libweston: rename weston_output_destroy() to weston_output_release()

'release' is a more appropriate name because the function does not free
the underlying memory. The main reason for this is that we need the name
weston_output_destroy() for new API that actually will free also the
underlying memory.

Since the function is only used in backends and external backends are
not a thing, this does not cause libweston major version bump, even
though it does change the ABI. There is no way external users could have
successfully used this function.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Ian Ray <ian.ray@ge.com>
Acked-by Daniel Stone <daniels@collabora.com>
diff --git a/libweston/compositor.h b/libweston/compositor.h
index 804d091..8b2d2b0 100644
--- a/libweston/compositor.h
+++ b/libweston/compositor.h
@@ -1717,7 +1717,7 @@
 weston_output_move(struct weston_output *output, int x, int y);
 
 void
-weston_output_destroy(struct weston_output *output);
+weston_output_release(struct weston_output *output);
 void
 weston_output_transform_coordinate(struct weston_output *output,
 				   double device_x, double device_y,