Upgrade libevent

diff --git a/lib b/lib
index 1c060834d468caf5a3c1f3c312cad9b3b10beb89..a8667935819d50719c7f049206418e9f07e447d0 160000 (submodule)
--- a/lib
+++ b/lib
@@ -1 +1 @@
-Subproject commit 1c060834d468caf5a3c1f3c312cad9b3b10beb89
+Subproject commit a8667935819d50719c7f049206418e9f07e447d0