[PATCH] emacs: Use `cl-lib' instead of deprecated `cl'

[Jonas Bernoulli]

I have fixed the remaining issues and added two small commits.
See v3.  

> Or of course you can/should get the tests running locally.

The problem was that there are incompatible changes in Emacs 27.
I am using Emacs 26 for the time being but will look into these
breaking changes later.  The first one was easy to work around,
but that just revealed a second one... 

  Jonas