unix: define IfMsghdr2, IfData64, and RtMsghdr2 on darwin

Change-Id: I6943f6b5bd9f7d0ef5bad24ed638b8cf5dd0353d
Reviewed-on: https://go-review.googlesource.com/c/sys/+/633077
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

Author: ianlancetaylor

unix/types_darwin.go

@@ -256,18 +256,25 @@ type FdSet C.fd_set
 
 const (
 	SizeofIfMsghdr    = C.sizeof_struct_if_msghdr
+	SizeofIfMsghdr2   = C.sizeof_struct_if_msghdr2
 	SizeofIfData      = C.sizeof_struct_if_data
+	SizeofIfData64    = C.sizeof_struct_if_data64
 	SizeofIfaMsghdr   = C.sizeof_struct_ifa_msghdr
 	SizeofIfmaMsghdr  = C.sizeof_struct_ifma_msghdr
 	SizeofIfmaMsghdr2 = C.sizeof_struct_ifma_msghdr2
 	SizeofRtMsghdr    = C.sizeof_struct_rt_msghdr
+	SizeofRtMsghdr2   = C.sizeof_struct_rt_msghdr2
 	SizeofRtMetrics   = C.sizeof_struct_rt_metrics
 )
 
 type IfMsghdr C.struct_if_msghdr
 
+type IfMsghdr2 C.struct_if_msghdr2
+
 type IfData C.struct_if_data
 
+type IfData64 C.struct_if_data64
+
 type IfaMsghdr C.struct_ifa_msghdr
 
 type IfmaMsghdr C.struct_ifma_msghdr
@@ -276,6 +283,8 @@ type IfmaMsghdr2 C.struct_ifma_msghdr2
 
 type RtMsghdr C.struct_rt_msghdr
 
+type RtMsghdr2 C.struct_rt_msghdr2
+
 type RtMetrics C.struct_rt_metrics
 
 // Berkeley packet filter