Updates to Brotli compression format, decoder and encoder

This commit contains a batch of changes that were made to the Brotli
compression algorithm in the last month. Most important changes:

   * Fixes to the spec.
   * Change of code length code order.
   * Use a 2-level Huffman lookup table in the decoder.
   * Faster uncompressed meta-block decoding.
   * Optimized encoding of the Huffman code.
   * Detection of UTF-8 input encoding.
   * UTF-8 based literal cost modeling for improved
     backward reference selection.

brotli/enc/literal_cost.h

@@ -26,7 +26,12 @@ namespace brotli {
 // ringbuffer (data, mask) will take entropy coded and writes these estimates
 // to the ringbuffer (cost, mask).
 void EstimateBitCostsForLiterals(size_t pos, size_t len, size_t mask,
-                                 const uint8_t *data, float *cost);
+                                 const uint8_t *data,
+                                 float *cost);
+
+void EstimateBitCostsForLiteralsUTF8(size_t pos, size_t len, size_t mask,
+                                     const uint8_t *data,
+                                     float *cost);
 
 }  // namespace brotli