registry.el and gnus-registry.el ERT compatibility fixes, proto-stream.el commit revert, old .eld gnus-registry.el importer
* proto-stream.el (gnutls-negotiate): Revert inadvertent commit of the
version from the Claudio Bley GnuTLS patch (extra optional parameters
and host name).
* registry.el: Don't use ERT if it's not available.
* gnus-registry.el: Don't use ERT if it's not available.
(gnus-registry-delete-entries): New convenience function.
(gnus-registry-import-eld): Import from old .eld registry.