Update dependencies

vendor/github.com/alexbrainman/sspi/buffer.go

@@ -0,0 +1,57 @@
+// Copyright 2015 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.
+
+// +build windows
+
+package sspi
+
+import (
+	"io"
+	"unsafe"
+)
+
+func (b *SecBuffer) Set(buftype uint32, data []byte) {
+	b.BufferType = buftype
+	if len(data) > 0 {
+		b.Buffer = &data[0]
+		b.BufferSize = uint32(len(data))
+	} else {
+		b.Buffer = nil
+		b.BufferSize = 0
+	}
+}
+
+func (b *SecBuffer) Free() error {
+	if b.Buffer == nil {
+		return nil
+	}
+	return FreeContextBuffer((*byte)(unsafe.Pointer(b.Buffer)))
+}
+
+func (b *SecBuffer) Bytes() []byte {
+	if b.Buffer == nil || b.BufferSize <= 0 {
+		return nil
+	}
+	return (*[(1 << 31) - 1]byte)(unsafe.Pointer(b.Buffer))[:b.BufferSize]
+}
+
+func (b *SecBuffer) WriteAll(w io.Writer) (int, error) {
+	if b.BufferSize == 0 || b.Buffer == nil {
+		return 0, nil
+	}
+	data := b.Bytes()
+	total := 0
+	for {
+		n, err := w.Write(data)
+		total += n
+		if err != nil {
+			return total, err
+		}
+		if n >= len(data) {
+			break
+		}
+		data = data[n:]
+	}
+	return total, nil
+}