CRC32 compatible with pkzip, etc.

Hi,

Would you guys consider adding in a checksum algorithm option? Perhaps
like the --algorithm option in the below:

  http://www.research.att.com/sw/tools/uwin/man/man1/md5sum.html

In particular, I'd like an option to compute CRC's with the method used
in pkzip. I would also be willing to do the coding for this, but want to
see if this feature would be accepted before I start putting any work
into it.

Thanks,
Jeremy