Propagate OPER

Propagate OPER

Move opername and privset storage to struct User, so it can exist for
remote opers.

On /oper and when bursting opers, send:

    :foo OPER opername privset

which sets foo's opername and privset. The contents of the privset on
remote servers come from the remote server's config, so the potential
for confusion exists if these do not match.

If an oper's privset does not exist on a server that sees it, it will
complain, but create a placeholder privset. If the privset is created by
a rehash, this will be reflected properly.

/privs is udpated to take an optional argument, the server to query, and
is now local by default:

    /privs [[nick_or_server] nick]