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-rdp.c b/libweston/compositor-rdp.c
index f2fa0f4..393c118 100644
--- a/libweston/compositor-rdp.c
+++ b/libweston/compositor-rdp.c
@@ -570,7 +570,7 @@
 	struct rdp_output *output = to_rdp_output(base);
 
 	rdp_output_disable(&output->base);
-	weston_output_destroy(&output->base);
+	weston_output_release(&output->base);
 
 	free(output);
 }
@@ -1360,7 +1360,7 @@
 err_listener:
 	freerdp_listener_free(b->listener);
 err_output:
-	weston_output_destroy(&b->output->base);
+	weston_output_release(&b->output->base);
 err_compositor:
 	weston_compositor_shutdown(compositor);
 err_free_strings: