switch kr/pty to creack/pty v1.1.7

kr/pty was moved to creak/pty and the old location was
archived.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/github.com/creack/pty/pty_openbsd.go

@@ -0,0 +1,33 @@
+package pty
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+func open() (pty, tty *os.File, err error) {
+	/*
+	 * from ptm(4):
+	 * The PTMGET command allocates a free pseudo terminal, changes its
+	 * ownership to the caller, revokes the access privileges for all previous
+	 * users, opens the file descriptors for the pty and tty devices and
+	 * returns them to the caller in struct ptmget.
+	 */
+
+	p, err := os.OpenFile("/dev/ptm", os.O_RDWR|syscall.O_CLOEXEC, 0)
+	if err != nil {
+		return nil, nil, err
+	}
+	defer p.Close()
+
+	var ptm ptmget
+	if err := ioctl(p.Fd(), uintptr(ioctl_PTMGET), uintptr(unsafe.Pointer(&ptm))); err != nil {
+		return nil, nil, err
+	}
+
+	pty = os.NewFile(uintptr(ptm.Cfd), "/dev/ptm")
+	tty = os.NewFile(uintptr(ptm.Sfd), "/dev/ptm")
+
+	return pty, tty, nil
+}