Define list thing to improve navigation in Emacs 31

[rrudakov]

If list thing is defined, Emacs 31 will set a few options automatically to improve navigation by lists/sexp etc.

Big thanks for the patch to Juri Linkov [email protected].

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Thanks!

[bbatsov]

Let's also add a Caveats section in the README where we can gather up items like these, so people are not surprised by differences in the behavior on different versions of Emacs.

[bbatsov]

(I added the section, so you can just an item there)

[rrudakov]

We can also set forward-sexp-function to nil if Emacs version is < 31 to workaround the bug #62

[rrudakov]

Let's also add a Caveats section in the README where we can gather up items like these, so people are not surprised by differences in the behavior on different versions of Emacs.

Done.

[bbatsov]

Thanks!