First split into crockery init and crockery run

The init command creates a crockery.db file containing the domain name and
TLS keypair. The run command starts IMAP and SMTP services based on that file.

Supporting only a single domain is starting to look a bit unnecessary. We'll
see how that goes.

vendor/golang.org/x/sys/unix/dev_openbsd.go

@@ -0,0 +1,29 @@
+// Copyright 2017 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.
+
+// Functions to access/create device major and minor numbers matching the
+// encoding used in OpenBSD's sys/types.h header.
+
+package unix
+
+// Major returns the major component of an OpenBSD device number.
+func Major(dev uint64) uint32 {
+	return uint32((dev & 0x0000ff00) >> 8)
+}
+
+// Minor returns the minor component of an OpenBSD device number.
+func Minor(dev uint64) uint32 {
+	minor := uint32((dev & 0x000000ff) >> 0)
+	minor |= uint32((dev & 0xffff0000) >> 8)
+	return minor
+}
+
+// Mkdev returns an OpenBSD device number generated from the given major and minor
+// components.
+func Mkdev(major, minor uint32) uint64 {
+	dev := (uint64(major) << 8) & 0x0000ff00
+	dev |= (uint64(minor) << 8) & 0xffff0000
+	dev |= (uint64(minor) << 0) & 0x000000ff
+	return dev
+}