cryptopp's config.h has the following pragma:
#pragma GCC diagnostic ignored "-Wunused-function"
It is not wrapped in a push/pop. Because of that, including cryptopp
headers disables that warning on scylla code too.
The issue has been reported as
https://github.com/weidai11/cryptopp/issues/793
To work around it, this patch uses a pimpl to have a single .cc file
that has to include cryptopp headers.
While at it, it also reduces the differences and code duplication
between the md5 and sha1 hashers.
Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>
