build: Stop relying on OpenSSL

The OpenSSL dependency was added for one program, fssum, and it needs
it only because it needs a md5 implementation.  Use Solar Designer's
openssl compatible implementation of md5 so we no longer need to
depend on OpenSSL.

Since the OpenSSL libraries are not always available, we had to add
extra complexity to test to see whether fssum exists.

The other problem with depending on the OpenSSL libraries is that
shared library compatibility situation is terrible; a fssum binary
built on a system using libssl1.0.0 is *NOT* run on a system with
libssl1.0.2, since the shared libraries are incompatible even across a
minor version bump.  (Sigh.)

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
8 files changed