Bump libusual

diff --git a/lib b/lib
index 64000c3bf99c1eb3a272bd266083ba3d033a7fcb..56b3e73181c1682375481b607a35d813cac84382 160000 (submodule)
--- a/lib
+++ b/lib
@@ -1 +1 @@
-Subproject commit 64000c3bf99c1eb3a272bd266083ba3d033a7fcb
+Subproject commit 56b3e73181c1682375481b607a35d813cac84382