Allow HMAC operations to work in FIPS mode
Allow symmetric key ciphers to work in FIPS mode

This is a first version, in which aes_ctr stream mode is
disabled. Although this cipher is FIPS verified, the interface between
the Erlang and NIF code needs to be rewritten, which will be addressed
by a later commit.
Allow querying FIPS mode status at runtime
Return notsup for disabled algorithms in FIPS mode

The old behaviour was to raise a badarg error from the NIF. The new
behaviour is more consistent with the way compile-time disabled
algorithms are handled.