crc32c 0.6.8 Zlib-derived combine implementation

The exact source comment documents the C-to-Rust translation and polynomial change:

//! Implements the CRC32c "combine" function, which calculates the CRC32c of two byte streams
//! concatenated together using their individual CRC32c values (plus the length of the second byte
//! stream).
//!
//! This module is essentially a line-by-line translation of ZLIB's CRC "combine" function
//! implementation from C to Rust, except for the CRC polynomial used (original uses the CRC32
//! polynomial 0xedb88320UL, we use the CRC32c polynomial 0x82F63B78).
//!
//! Link to original implementation: https://github.com/madler/zlib/blob/master/crc32.c
//!
//! This file is based on the Zlib project, located at: https://github.com/madler/zlib,
//! which includes the following notice:
//!
//! crc32.c -- compute the CRC-32 of a data stream
//! Copyright (C) 1995-2006, 2010, 2011, 2012, 2016 Mark Adler
//! For conditions of distribution and use, see copyright notice in zlib.h
//!
//! Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
//! CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
//! tables for updating the shift register in one step with three exclusive-ors
//! instead of four steps with four exclusive-ors.  This results in about a
//! factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.

Corresponding upstream Zlib license, from zlib.h at tag v1.2.11:
https://github.com/madler/zlib/blob/v1.2.11/zlib.h
Full source SHA-256: 4ddc82b4af931ab55f44d977bde81bfbc4151b5dcdccc03142831a301b5ec3c8

/* zlib.h -- interface of the 'zlib' general purpose compression library
  version 1.2.11, January 15th, 2017

  Copyright (C) 1995-2017 Jean-loup Gailly and Mark Adler

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  Jean-loup Gailly        Mark Adler
  jloup@gzip.org          madler@alumni.caltech.edu


  The data format used by the zlib library is described by RFCs (Request for
  Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
  (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
*/
