c/ontrol: d/rules: d/libstrongswan-extra-plugins.install: add NTRU (key...

Hi, this change: "d/control: d/rules: d/libstrongswan-extra-plugins.install: add NTRU (key exchanged based on post-quantum computer NTRU) plugin based on user request" was triggered by LP 1863749.

A while ago we synced so much (thanks again) between Ubuntu and Debian packaging and enabled a lot on Debian that were nto enabled before, while at the other hand disabled a lot of plugins that we expected to be unused.

Now this issue came up and I guess NTRU might actually be of use. Reading into the topic its base makes sense and looking e.g. a decade into the future people might actually be interested in more quantum-computer-safety. I guess today no one knows if it really is safer, but at least there are no known attacks yet while the attacks exist for other key algorithms.

So it made sense to me, therefore I should just enable it in Ubuntu right. Well I want to do better than the past before the two of us started to work together on improving both, therefore I thought I'm proposing the change here to discuss and go with the change together.

Please let me know what you think of NTRU and if you'd be ok to enable it in libstrongswan-extra-plugins (while it seems used, it still is -extra IMHO).