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 three weeks. Most important changes:

  * Added UTF8 context model for good text compression.
  * Simplified context modeling by having only 4 context modes.
  * Per-block context mode selection.
  * Faster backward copying and bit reading functions.
  * More efficient histogram coding.
  * Streaming support for the decoder and encoder.

brotli/dec/huffman.h

@@ -43,7 +43,6 @@ struct HuffmanTree {
   HuffmanTreeNode* root_;   // all the nodes, starting at root.
   int max_nodes_;           // max number of nodes
   int num_nodes_;           // number of currently occupied nodes
-  int fixed_bit_length_;     // If non-zero, uses fixed length coding
 };
 
 // Returns true if the given node is not a leaf of the Huffman tree.
@@ -65,19 +64,9 @@ void BrotliHuffmanTreeRelease(HuffmanTree* const tree);
 // Builds Huffman tree assuming code lengths are implicitly in symbol order.
 // Returns false in case of error (invalid tree or memory error).
 int BrotliHuffmanTreeBuildImplicit(HuffmanTree* const tree,
-                                   const int* const code_lengths,
+                                   const uint8_t* const code_lengths,
                                    int code_lengths_size);
 
-// Build a Huffman tree with explicitly given lists of code lengths, codes
-// and symbols. Verifies that all symbols added are smaller than max_symbol.
-// Returns false in case of an invalid symbol, invalid tree or memory error.
-int BrotliHuffmanTreeBuildExplicit(HuffmanTree* const tree,
-                                   const int* const code_lengths,
-                                   const int* const codes,
-                                   const int* const symbols,
-                                   int max_symbol,
-                                   int num_symbols);
-
 #if defined(__cplusplus) || defined(c_plusplus)
 }    // extern "C"
 #endif