syscall: add MSG_FASTOPEN to Linux

Update #4842

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7369060

src/pkg/syscall/mkerrors.sh

@@ -83,6 +83,10 @@ includes_Linux='
 #include <net/if_arp.h>
 #include <net/route.h>
 #include <netpacket/packet.h>
+
+#ifndef MSG_FASTOPEN
+#define MSG_FASTOPEN    0x20000000
+#endif
 '
 
 includes_NetBSD='

src/pkg/syscall/zerrors_linux_386.go

@@ -528,6 +528,7 @@ const (
 	MSG_DONTWAIT                     = 0x40
 	MSG_EOR                          = 0x80
 	MSG_ERRQUEUE                     = 0x2000
+	MSG_FASTOPEN                     = 0x20000000
 	MSG_FIN                          = 0x200
 	MSG_MORE                         = 0x8000
 	MSG_NOSIGNAL                     = 0x4000

src/pkg/syscall/zerrors_linux_amd64.go

@@ -528,6 +528,7 @@ const (
 	MSG_DONTWAIT                     = 0x40
 	MSG_EOR                          = 0x80
 	MSG_ERRQUEUE                     = 0x2000
+	MSG_FASTOPEN                     = 0x20000000
 	MSG_FIN                          = 0x200
 	MSG_MORE                         = 0x8000
 	MSG_NOSIGNAL                     = 0x4000

src/pkg/syscall/zerrors_linux_arm.go

@@ -523,6 +523,7 @@ const (
 	MSG_DONTWAIT                     = 0x40
 	MSG_EOR                          = 0x80
 	MSG_ERRQUEUE                     = 0x2000
+	MSG_FASTOPEN                     = 0x20000000
 	MSG_FIN                          = 0x200
 	MSG_MORE                         = 0x8000
 	MSG_NOSIGNAL                     = 0x4000