Log Message:
gsasl: update to 1.8.1.

* Version 1.8.1 (released 2019-08-02) [stable]

** gsasl: IMAP client code now permits empty SASL tokens prefixed with '+'.
Normally servers should send '+ '.  Buggy servers include Microsoft
Exchange.  Reported by Adam Sjøgren.

** GSSAPI client: Now retrieves GSASL_AUTHZID for authorization identity.
** GSSAPI client: Can now transmit an empty/missing authorization identity.
See lib/NEWS for more information.

** Build fixes.
Update of gnulib, including how it is bootstrapped.

** i18n: Updated translations.