[dev.cc] runtime: convert openbsd/amd64 port to Go

LGTM=rsc
R=rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/171660043
diff --git a/src/runtime/os2_openbsd.go b/src/runtime/os2_openbsd.go
new file mode 100644
index 0000000..1e785ad
--- /dev/null
+++ b/src/runtime/os2_openbsd.go
@@ -0,0 +1,14 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+const (
+	_SS_DISABLE  = 4
+	_SIG_BLOCK   = 1
+	_SIG_UNBLOCK = 2
+	_SIG_SETMASK = 3
+	_NSIG        = 33
+	_SI_USER     = 0
+)