Major changes, including Brotli and Lizard

- update of zstd-mt library
- add brotli v0.6.0
- add lizard v2.0
- xxhash is from zstd for lz4, lz5 and lizard now
- update also the documentation, where needed

C/brotli/br_bit_cost.c

@@ -0,0 +1,35 @@
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Functions to estimate the bit cost of Huffman trees. */
+
+#include "./enc/bit_cost.h"
+
+#include "./common//constants.h"
+#include "types.h"
+#include "./enc/fast_log.h"
+#include "./enc/histogram.h"
+#include "./enc/port.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+#define FN(X) X ## Literal
+#include "./enc/bit_cost_inc.h"  /* NOLINT(build/include) */
+#undef FN
+
+#define FN(X) X ## Command
+#include "./enc/bit_cost_inc.h"  /* NOLINT(build/include) */
+#undef FN
+
+#define FN(X) X ## Distance
+#include "./enc/bit_cost_inc.h"  /* NOLINT(build/include) */
+#undef FN
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}  /* extern "C" */
+#endif