Rename md5ChunkSize to HASH_READ_CHUNK_SIZE and remove the unused crc32ChunkSize as the same read chunk is used for both hashes. Increase the chunk size from 10KB to 32KB. Optimize CRC32 inner loop to avoid calling the length message for each byte. Together these changes reduce total hash calculation time by about 20% when reading from an SSD.
Merge pull request #1134 from joewreschnig/master

Avoid per-byte ObjC message when importing (~20% faster)