blake2b: new package

Add the hash function BLAKE2b defined in RFC 7693.

On amd64/AVX2
name 		time/op
Write128-4 	164ns ± 1%
Write1K-4 	1.19µs ± 2%
Sum128-4 	187ns ± 1%
Sum1K-4 	1.21µs ± 1%

name 		speed
Write128-4 	800MB/s ± 1%
Write1K-4 	856MB/s ± 2%
Sum128-4 	682MB/s ± 1%
Sum1K-4     	842MB/s ± 1%

On amd64/SSE4
name 		time/op
Write128-4 	192ns ± 1%
Write1K-4 	1.37µs ± 0%
Sum128-4 	215ns ± 1%
Sum1K-4 	1.39µs ± 1%

name 		speed
Write128-4 	665MB/s ± 1%
Write1K-4 	746MB/s ± 0%
Sum128-4 	592MB/s ± 1%
Sum1K-4 	735MB/s ± 1%

Change-Id: I0b41ae136980b0e8a970be330e8cc5f02b9e6818
Reviewed-on: https://go-review.googlesource.com/30918
Reviewed-by: Adam Langley <agl@golang.org>
diff --git a/blake2b/blake2b_ref.go b/blake2b/blake2b_ref.go
new file mode 100644
index 0000000..da156a1
--- /dev/null
+++ b/blake2b/blake2b_ref.go
@@ -0,0 +1,11 @@
+// Copyright 2016 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 !amd64 appengine gccgo
+
+package blake2b
+
+func hashBlocks(h *[8]uint64, c *[2]uint64, flag uint64, blocks []byte) {
+	hashBlocksGeneric(h, c, flag, blocks)
+}