Update libc version

Has the required constants and symbols for OpenBSD.

Author: Thomasdezeeuw

Cargo.toml

@@ -20,7 +20,7 @@ default = []
 nightly = []
 
 [dependencies]
-libc         = { version = "0.2.179", default-features = false }
+libc         = { version = "0.2.181", default-features = false }
 log          = { version = "0.4.21",  default-features = false, features = ["kv_std"] }
 
 [dev-dependencies]