CRC algorithm code taken from CRC-32 by Craig Bruce. 
The module stuff is inspired by a similar perl module called 
String::CRC by David Sharnoff & Matthew Dillon.
Horst Fickenscher told me that it could be useful to supply an init
value to the crc checking function and so I included this possibility.

The author of this package disclaims all copyrights and 
releases it into the public domain.