various fixes for parse-dla.pl

The following are various fixes for parse-dla.pl to allow it to parse both emails from the mailing list archive (as found on master.debian.org) and emails templates generated from gen-DLA in the current security tracker.

This is how !41 (merged) and !42 (merged) were generated. Obviously, I will not create a merge request for each missing advisory, those are just first tests before I batch all changes into one gigantic merge request of death. ;)

Eventually, I'll figure out if the script can be used to parse all missing entries from the website, and this should eventually close this bug report:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=859122

I will also enquire with the LTS team to see if our process can be changed so that we can submit entries to you here directly, but we need to figure out what the best workflow would be.

I suspect it might be possible to setup a mailbox that would automatically parse incoming emails and add them to this repository, or something to that effect. That would be ideal as it would reduce the number of manual steps needed to publish those things. Failing that, I'm worried we would again get into a situation where we are desynchronized again. But that's best kept to the bug report about automating this process, here:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=859123

Cheers!