Fix CVE-2021-39359 by forcing TLS certificate validation
This was done by adding "ssl-use-system-ca-file", TRUE to the options for each soup_session_new_with_options() call that was made.
Note that the CI failure for 'parallel build' seems to be transient, I compared the results to some of the other recent commits and they seemed to be OK.
Tested on Linux From Scratch 11.0 and Debian 11.
Fixes #249 (closed)