Clean up inactive issues

There are a lot of open issues in this repo, but lots of there are just simply abandoned, not bugs or something. I suggest closing issues which have been inactive for a long time. These are easily found through sorting by least recently updated. I suggest closing issues which come up there which are older than ~2 months. Of course, also read through them a bit and use common sense.

This piece of text could be added as a comment:

> I’m closing this issue because it has been inactive for a few months. This probably means that it is not reproducible, it has been fixed in a newer version, or the issuer did not reply.
> Please reopen if you still encounter this issue with the latest stable version.
> Thank you!