Update mail to 2.7.1, pin sqlite3
Adapt one test-file to meet the new habit of 'mail' to output carriage returns.
Reworked the whole test-file to not use the custom smtp daemon, and to not run a sub-shell, in order to improve the speed and reduce possible side effects.
This also fixes the list-factory to include :sig
and :enc
in their headers_to_meta
.