bug#43275: Upgrade antlr-mode to latest version

[Wedler, Christoph]

Stefan Kangas <stefan@marxist.se> writes:

> I see now that there have been some changes in antlr-mode.el in the
> Emacs source tree.  None of them look very big to me, and I would expect
> that they would not take too much time for you to review.

> Would you be willing to merge those changes into your version and send
> an updated version here?

OK - I would basically do M-x emerge-files-with-ancestor:

- A: my antlr-mode.el 3.1.5
- B: lisp/progmodes/antlr-mode.el
- Ancestor: lisp/progmodes/antlr-mode.el.~emacs-25.1~ (see my ChangeLog comment 
2016-11-22),

Does that sounds reasonable?

If someone can guide me how Emacs handles git, I can probably directly push a 
change

- starting at branch "master"?
- which branch to push to?
- change comment: my ChangeLog starting at 2.2c?