Add option to stop connection if SASL authentication fails (irc.server.*.sasl_disconnect_on_fail).

See <https://savannah.nongnu.org/task/?12204>.

This also adds support for the 902 numeric (`ERR_NICKLOCKED`), which is used if SASL authentication fails because an account is frozen, locked or held.
Updated second array too. Didn't notice this in my tests because the next value is "off" too.