unix: regenerate all definitions on FreeBSD 12.1 on {386,amd64,arm64}

I just created a couple of virtual machines/QEMU instances containing
stock copies of FreeBSD 12.1-RELEASE. On these systems I ran mkall.sh,
thereby bringing the definitions in sync with that version of FreeBSD.

I also attempted to bring the GOOS=freebsd GOARCH=arm port up to date,
but was unfortunately not able to do so. There doesn't seem to be any
documentation on how to bring this port of FreeBSD up on an emulator.
The only option seems to be to use physical hardware.

Change-Id: I54c9f5d15587996ad5fbb535480ab0aa0e723260
GitHub-Last-Rev: ad79b1bda1307eb231b8e034dd15599e333ad25e
GitHub-Pull-Request: golang/sys#63
Reviewed-on: https://go-review.googlesource.com/c/sys/+/223698
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

unix/errors_freebsd_amd64.go

@@ -8,6 +8,7 @@
 package unix
 
 const (
+	DLT_HHDLC                         = 0x79
 	IFF_SMART                         = 0x20
 	IFT_1822                          = 0x2
 	IFT_A12MPPSWITCH                  = 0x82
@@ -210,13 +211,18 @@ const (
 	IFT_XETHER                        = 0x1a
 	IPPROTO_MAXID                     = 0x34
 	IPV6_FAITH                        = 0x1d
+	IPV6_MIN_MEMBERSHIPS              = 0x1f
 	IP_FAITH                          = 0x16
+	IP_MAX_SOURCE_FILTER              = 0x400
+	IP_MIN_MEMBERSHIPS                = 0x1f
 	MAP_NORESERVE                     = 0x40
 	MAP_RENAME                        = 0x20
 	NET_RT_MAXID                      = 0x6
 	RTF_PRCLONING                     = 0x10000
 	RTM_OLDADD                        = 0x9
 	RTM_OLDDEL                        = 0xa
+	RT_CACHING_CONTEXT                = 0x1
+	RT_NORTREF                        = 0x2
 	SIOCADDRT                         = 0x8040720a
 	SIOCALIFADDR                      = 0x8118691b
 	SIOCDELRT                         = 0x8040720b