Update libusual

diff --git a/lib b/lib
index 9d1ffbb5f4d74ebc35b439686ca10518c8fba2a2..51d444927e55fed0523e03dd17b392fc70556023 160000 (submodule)
--- a/lib
+++ b/lib
@@ -1 +1 @@
-Subproject commit 9d1ffbb5f4d74ebc35b439686ca10518c8fba2a2
+Subproject commit 51d444927e55fed0523e03dd17b392fc70556023