crypto/{md5,sha1,sha256,sha512} tests: Add benchmarks

[Bruno Haible]

It is to be expected that crypto hardware would not only speed up
sha1_stream but also sha1_buffer (where the input is in memory).

As a first step towards this, I'm adding benchmarks of the sha1_buffer etc.
functions.

The way to use this benchmark is, from a testdir:
$ gltests/bench-sha1 100000 100
which will run 100 repetitions of sha1_buffer on a memory region of size 100000.


2018-05-06 Bruno Haible <***@clisp.org>

crypto/{md5,sha1,sha256,sha512} tests: Add benchmarks.
* tests/bench-digest.h: New file.
* tests/bench-md5.c: New file.
* tests/bench-sha1.c: New file.
* tests/bench-sha224.c: New file.
* tests/bench-sha256.c: New file.
* tests/bench-sha384.c: New file.
* tests/bench-sha512.c: New file.
* modules/crypto/md5-tests (Files): Add tests/bench-md5.c,
tests/bench-digest.h.
(Depends-on): Add getrusage, gettimeofday.
(Makefile.am): Add variables to build bench-md5.
* modules/crypto/sha1-tests (Files): Add tests/bench-sha1.c,
tests/bench-digest.h.
(Depends-on): Add getrusage, gettimeofday.
(Makefile.am): Add variables to build bench-sha1.
* modules/crypto/sha256-tests (Files): Add tests/bench-sha224.c,
tests/bench-sha256.c, tests/bench-digest.h.
(Depends-on): Add getrusage, gettimeofday.
(Makefile.am): Add variables to build bench-sha224, bench-sha256.
* modules/crypto/sha512-tests (Files): Add tests/bench-sha384.c,
tests/bench-sha512.c, tests/bench-digest.h.
(Depends-on): Add getrusage, gettimeofday.
(Makefile.am): Add variables to build bench-sha384, bench-sha512.