Refresh libusual

diff --git a/lib b/lib
index 55587de13d870b41878bb4c7c94139fe97cb7a96..39c15f18621adc36954870ab6dcd65bfe167bf18 160000 (submodule)
--- a/lib
+++ b/lib
@@ -1 +1 @@
-Subproject commit 55587de13d870b41878bb4c7c94139fe97cb7a96
+Subproject commit 39c15f18621adc36954870ab6dcd65bfe167bf18