Evaluate J through emacs dynamic modules and libj.so.

I wrote this for fun and because I was getting fed up with how j-mode and org-babel interact. The code right now is usable for me but there are many ways it sucks, so I’d caution others against using it.

Lowlights

• J->emacs & emacs->J: marshall data between J and emacs.
• calculator: access J prompt in the mini bar through key binding <kbd>M-j</kbd>.
• viewmat: if the viewmat.png file changes from executing some J, a buffer pops up to display it inside emacs.
• plot: if the plot.pdf file changes from executing some J, the buffer is opened and viewed through pdf-tools.
• ob-jpl: facilities for using jpl-mode in org mode.
• joogle: emacs procedure that prompts for a J token and opens the corresponding NuVoc page in a browser.
• font lock: correctly classifies J tokens by verb, adverb, conjunction, and so on (j-mode misidentifies things like : and a few others) and adds a colors for nouns and names. Basically, with for_a. i. 10 do. font-lock will recognize that a is a binding and color it, bindings such as \'a b\'=. y don’t get highlighted as strings, and things like a: and a. get their own color.
• pretty symbols: approximate J in APL glyphs through <kbd>M-p</kbd> and pretty symbol mode.

Warnings

• Using J in this way can cause segfaults (wip)!