This patch adds 3 new signals:
* tlsa avalable: emitted if TLSA is available for a given domain.
* tlsa verification success: emitted if the TLSA check was successful.
* tlsa verification failed: emitted if the TLSA check was unsuccessful.
git-svn-id: file:///var/www/svn.irssi.org/SVN/irssi/trunk@5220 dbcabf3a-b0e7-0310-adc4-f8d773084564