Implement indentation support for TeX-style literate Haskell buffers

[DataKinds]

This PR implements a new function haskell-indentation-literate-outside-code-p which may be used to detect when the point is outside a code block in both Bird-style and TeX-style literate buffers. Note that GHC accepts a mixture of both Bird-style and TeX-style delimiting in the same file, so changing the possible values of the haskell-literate variable might be in-scope here as well.

[purcell]

Thanks!

[purcell]

Hey @DataKinds, @smonnier suggests a simpler formulation of the new function:

(defun haskell-indentation-tex-outside-code-p ()
  "Non-NIL if we are in tex literate mode, but outside of code."
  (and (haskell-indentation-tex-p)
       (not (and (save-excursion
                   (re-search-backward "\\\\end{code}\\|\\\\begin{code}\\(\\)"
                                       nil t))
                 (match-end 1)))))

Would you mind testing it out to see if it works?

[DataKinds]

Hey @DataKinds, @smonnier suggests a simpler formulation of the new function:

(defun haskell-indentation-tex-outside-code-p ()
  "Non-NIL if we are in tex literate mode, but outside of code."
  (and (haskell-indentation-tex-p)
       (not (and (save-excursion
                   (re-search-backward "\\\\end{code}\\|\\\\begin{code}\\(\\)"
                                       nil t))
                 (match-end 1)))))

Would you mind testing it out to see if it works?

Tested both in and out of evil-mode on the same file I wrote my PR with. As far as I can tell the simpler formulation works well. The empty group at the end of the regex is a cool trick.