libgo/go/syscall: add SockAddrDatalink on AIX

    
    This patch is required in order to build golang.org/x/net. The
    corresponding Go Toolchain patch is CL 170537.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/172898

From-SVN: r270458

gcc/go/gofrontend/MERGE

-ecbd6562aff604b9559f63d714e922a0c9c2a77f
+1d2b98a4af0188f3f1d4a3eaae928e1db8383a63
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/syscall/socket_aix.go

@@ -11,6 +11,7 @@ import "unsafe"
 const SizeofSockaddrInet4 = 16
 const SizeofSockaddrInet6 = 28
 const SizeofSockaddrUnix = 1025
+const SizeofSockaddrDatalink = 128
 
 type RawSockaddrInet4 struct {
 	Len    uint8
@@ -87,3 +88,26 @@ func GetsockoptIPv6MTUInfo(fd, level, opt int) (*IPv6MTUInfo, error) {
 	err := getsockopt(fd, level, opt, unsafe.Pointer(&value), &vallen)
 	return &value, err
 }
+
+type SockaddrDatalink struct {
+	Len    uint8
+	Family uint8
+	Index  uint16
+	Type   uint8
+	Nlen   uint8
+	Alen   uint8
+	Slen   uint8
+	Data   [120]uint8
+	raw    RawSockaddrDatalink
+}
+
+type RawSockaddrDatalink struct {
+	Len    uint8
+	Family uint8
+	Index  uint16
+	Type   uint8
+	Nlen   uint8
+	Alen   uint8
+	Slen   uint8
+	Data   [120]uint8
+}