Move the optional output name property from drm_output to weston_output

In the future the CMS plugins will need to read the config file and setup a list
of hardcoded names to ICC profiles.
diff --git a/src/compositor.c b/src/compositor.c
index c1acd50..a6610e6 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -2908,6 +2908,7 @@
 
 	wl_signal_emit(&output->destroy_signal, output);
 
+	free(output->name);
 	pixman_region32_fini(&output->region);
 	pixman_region32_fini(&output->previous_damage);
 	output->compositor->output_id_pool &= ~(1 << output->id);