Issue #1288 - Part 1a: Update brotli to 1.0.7

This also reorganizes the exports in the build system to use `brotli/`
as include directory.

modules/brotli/enc/utf8_util.h

@@ -0,0 +1,32 @@
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Heuristics for deciding about the UTF8-ness of strings. */
+
+#ifndef BROTLI_ENC_UTF8_UTIL_H_
+#define BROTLI_ENC_UTF8_UTIL_H_
+
+#include "../common/platform.h"
+#include <brotli/types.h>
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+static const double kMinUTF8Ratio = 0.75;
+
+/* Returns 1 if at least min_fraction of the bytes between pos and
+   pos + length in the (data, mask) ring-buffer is UTF8-encoded, otherwise
+   returns 0. */
+BROTLI_INTERNAL BROTLI_BOOL BrotliIsMostlyUTF8(
+    const uint8_t* data, const size_t pos, const size_t mask,
+    const size_t length, const double min_fraction);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}  /* extern "C" */
+#endif
+
+#endif  /* BROTLI_ENC_UTF8_UTIL_H_ */