Use new libc version

nikklassen · nikklassen · commit 672189105515 · 2016-06-29T13:34:07.000-04:00
diff --git a/Cargo.toml b/Cargo.toml
@@ -23,7 +23,7 @@ preadv_pwritev = []
 signalfd = []
 
 [dependencies]
-libc = "0.2.11"
+libc = "0.2.13"
 bitflags = "0.4"
 cfg-if = "0.1.0"
 void = "1.0.2"
