Indicate whether to show plugin's inline display in GUI

This is currently done by an extension data similarly to
LV2_INLINEDISPLAY__interface.

libs/plugins/a-comp.lv2/a-comp.c

@@ -873,6 +873,9 @@ extension_data(const char* uri)
 	if (!strcmp(uri, LV2_INLINEDISPLAY__interface)) {
 		return &display;
 	}
+	if (!strcmp(uri, LV2_INLINEDISPLAY__in_gui)) {
+		return &display;
+	}
 #endif
 	return NULL;
 }