Use gnutls_rnd instead of gcry_randomize on newer GnuTLS versions.

Also, fix a bug where eval() caused compile errors.
Merge pull request #685 from SaberUK/master+gnutls-rng

Use gnutls_rnd instead of gcry_randomize on newer GnuTLS versions.
Disallow remote /MODULES for non-opers.
Allow multiple allowmasks in link blocks, #679