SASL: Smarter forming of default values
SASL: Smarter forming of default values

If the Authname is not given, use the username.
If the FQDN is not given, use the realm (if not empty).

Fixes: NB#218635 - Generates invalid DIGEST-MD5 responses for XMPP

plotters/accounts-sso.signond,maemo-foss/accounts-sso-signon,maemo-foss/accounts-sso-signon,plotters/accounts-sso.signond,plotters/accounts-sso.signond,maemo-foss/accounts-sso-signon