Fixes compile on glibc-2.25

Fixes: https://bugs.gentoo.org/612658
--- cfengine-3.6.2.orig/libutils/platform.h	2014-09-25 04:53:31.000000000 -0700
+++ cfengine-3.6.2/libutils/platform.h	2017-10-20 15:11:15.676360363 -0700
@@ -360,12 +360,13 @@ void globfree(glob_t *pglob);
 
 #ifdef __linux__
 # if defined(__GLIBC__) || defined(__BIONIC__)
 #  include <net/route.h>
 #  include <netinet/in.h>
 #  include <netinet/ip.h>
+#  include <sys/sysmacros.h>
 # else
 #  include <linux/route.h>
 #  include <linux/in.h>
 #  include <linux/ip.h>
 # endif
 #endif