b2sum source code and Autotools files

[Jeffrey Walton]

Hi Everyone/Ken,

BLAKE2's b2sum is available at https://github.com/BLAKE2/BLAKE2. In
particular, the latest tarball is available at
https://github.com/BLAKE2/BLAKE2/releases/tag/20190724. The 20190724
release includes SSE2, XOP, SSE4, AVX and NEON implementations.

There is an Autotools port from the makefiles to Autotools so
'configure && make && make check && make install' works as expected.
The files are available at https://github.com/BLAKE2/BLAKE2/pull/63. A
zip is available at https://github.com/BLAKE2/BLAKE2/issues/61. The
files are in public domain so there are no license encumbrances.

It should be fairly easy to add b2sum to MacPorts with the Autotools
front-end. (b2sum is currently missing from MacPorts).

Jeff