unix: add Uname on openbsd

Change-Id: I40f99aab912c7002d113f82ccc60c9f68b9bc496
Reviewed-on: https://go-review.googlesource.com/82855
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/zerrors_openbsd_arm.go

@@ -1,5 +1,5 @@
 // mkerrors.sh
-// MACHINE GENERATED BY THE COMMAND ABOVE; DO NOT EDIT
+// Code generated by the command above; see README.md. DO NOT EDIT.
 
 // Created by cgo -godefs - DO NOT EDIT
 // cgo -godefs -- _const.go
@@ -157,6 +157,8 @@ const (
 	CSTOP                             = 0x13
 	CSTOPB                            = 0x400
 	CSUSP                             = 0x1a
+	CTL_HW                            = 0x6
+	CTL_KERN                          = 0x1
 	CTL_MAXNAME                       = 0xc
 	CTL_NET                           = 0x4
 	DIOCOSFPFLUSH                     = 0x2000444e
@@ -441,6 +443,7 @@ const (
 	F_UNLCK                           = 0x2
 	F_WRLCK                           = 0x3
 	HUPCL                             = 0x4000
+	HW_MACHINE                        = 0x1
 	ICANON                            = 0x100
 	ICMP6_FILTER                      = 0x12
 	ICRNL                             = 0x100
@@ -859,6 +862,10 @@ const (
 	IXANY                             = 0x800
 	IXOFF                             = 0x400
 	IXON                              = 0x200
+	KERN_HOSTNAME                     = 0xa
+	KERN_OSRELEASE                    = 0x2
+	KERN_OSTYPE                       = 0x1
+	KERN_VERSION                      = 0x4
 	LCNT_OVERLOAD_FLUSH               = 0x6
 	LOCK_EX                           = 0x2
 	LOCK_NB                           = 0x4