Latex fixes

[dschrempf]

Hi! This fixes #1100; well, it disables some features of smartparens for latex modes. The PR also includes some other nits and changes. Let me know if I should exclude those.

Finally, this change is a breaking change for people using

(sp-local-pair modes "``" nil ...))) ;; or
(sp-local-pair modes "`" nil ...)))

For example, this affects Doom Emacs, which I am using. The corresponding patch for Doom Emacs is attached.
s.patch

[Fuco1]

Hmm, to be fair though, the "default" behaviour is fine until you use those special language quotes, right? I wonder if we shouldn't keep it working e.g. in english.

[dschrempf]

For me, smartparens is completely broken in LaTeX, also in English. I am not using German in my documents. It could be a Doom Emacs issue. I removed all the relevant changes (see the patch), but who knows.

[real-or-random]

This works for me (also on doom), and yes, letting AuCTeX handle quotes seems sensible.

And indeed, this solves a problem that is unrelated to German quotes, so the reference to #1100 may be a bit misleading. (To be honest, I don't know if this also solves #1100).

[real-or-random]

See doomemacs/doomemacs#8437 for workaround in Doom.

letting AuCTeX handle quotes seems sensible.

I'm not sure anymore. It's at least better than the current broken behavior. But ideally, we could get the best of both worlds, i.e., smartparens's automatic insertion of closing quotes and AucTeX's support for quotes.