warning: incompatible implicit declaration of built-in function 'strlen'

--- compat/getopt.c.orig	Sat May  2 10:41:42 2015
+++ compat/getopt.c	Sat May  2 10:42:21 2015
@@ -34,6 +34,8 @@
 #include <config.h>
 #endif
 
+#include <string.h>
+
 #if !defined (__STDC__) || !__STDC__
 /* This is a separate conditional since some stdc systems
    reject `defined (const)'.  */