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.