unix: add SetsockoptTCPRepairOpt on Linux

There is currently no function to allow for setting repair options for sockets in repair mode.
There are 4 options catered for in the linux implementation.

TCPOPT_WINDOW
TCPOPT_MAXSEG
TCPOPT_SACK_PERMITTED
TCPOPT_TIMESTAMP

Details of the patch to the kernel and the thinking behind it is here  https://lwn.net/Articles/495304

Work done in this commit
Included the tcp options type and length for inclusion in the Docker build
Added TCPOPT to the regular expression in mkerrors.sh. There was only TCP_ previously
Add the new function to syscall_unix.go

I have tested locally and verified each option with ss -i

I am not sure whether to commit tests because I don't know if socket creation is possible on the test runs in the offical pipeline.
I did check for existing tests but didn't see any that created sockets, only one that validated a string option.

Fixes golang/go#46984

Change-Id: Iade0434c05cebf2fbdfb5f04b2a7b51c8b358423
Reviewed-on: https://go-review.googlesource.com/c/sys/+/332709
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

unix/linux/types.go

@@ -637,6 +637,8 @@ type CanFilter C.struct_can_filter
 
 type ifreq C.struct_ifreq
 
+type TCPRepairOpt C.struct_tcp_repair_opt
+
 const (
 	SizeofSockaddrInet4     = C.sizeof_struct_sockaddr_in
 	SizeofSockaddrInet6     = C.sizeof_struct_sockaddr_in6
@@ -673,6 +675,7 @@ const (
 	SizeofUcred             = C.sizeof_struct_ucred
 	SizeofTCPInfo           = C.sizeof_struct_tcp_info
 	SizeofCanFilter         = C.sizeof_struct_can_filter
+	SizeofTCPRepairOpt      = C.sizeof_struct_tcp_repair_opt
 )
 
 // Netlink routing and interface messages