Previously it was declared to be an instance of block-checksum, which is
not necessarily the case, since the participating checksums don't have to
be block-checksums.
It's probably bad to have the year in the license file, but it's worse to depend on
the license never changing.
Add a dummy file to crc32, and for multi checksums, the file we were checksumming is
not really integral to the test since it's read into a buffer first.
John Benediktsson
Alexander Iljin
Doug Coleman