Investigate OpenSSL dependency

As far as I understand, OpenSSL is only used in this library for the `multiexp_profile` flag, but in that case why is it needed? Can we remove the dependency?

At a glance, I don't see why https://github.com/scipr-lab/libff/blob/master/libff/algebra/scalar_multiplication/multiexp_profile.cpp needs openSSL. 