Add support for various SHA checksum digests

Add support for various SHA checksum digests

The main purpose of the SHA checksums are to allow the daemon auth code
to pick a stonger digest method when negotiating the auth digest to use.
However, the SHA digests are also available for use in file checksums,
should someon really want to use one of them.

The new digests are listed from strongest to weakest at the start of the
daemon auth list, giving them the highest priority.

The new digests are listed from weakest to strongest near the end of the
checksum list, giving them the lowest priority of use for file
checksums.