add CLONE_NEWCGROUP clone flag, new in linux v4.6

flag for new cgroup namespace, added in linux commit
5e2bec7c2248ae27c5b16cd97215ae05c1d39179

include/sched.h

@@ -59,6 +59,7 @@ int     sched_yield(void);
 #define CLONE_DETACHED	0x00400000
 #define CLONE_UNTRACED	0x00800000
 #define CLONE_CHILD_SETTID	0x01000000
+#define CLONE_NEWCGROUP	0x02000000
 #define CLONE_NEWUTS	0x04000000
 #define CLONE_NEWIPC	0x08000000
 #define CLONE_NEWUSER	0x10000000