Reverse byte order for specific datum sizes. Note that the byte-swap approach avoids alignment issues, so is probably faster overall than a traditional 'shift' implementation.
Tango Dual License: 3-Clause BSD License / Academic Free License v3.0. See LICENSE_TANGO.txt for details.
Copyright (c) 2004 Kris Bell. Some parts copyright (c) 2009-2016 dunnhumby Germany GmbH. All rights reserved.
Initial release: October 2004 Feb 20th 2005 - Asm version removed by Aleksey Bobnev