Emacs sync 2

[dgutov]

This is another sync of the current progress.

• Brought back highlighting of assignments.
• Added a bunch of other highlightings
• Reworked the indentation rules to handle certain edge cases and support all latest ruby-mode's indentation options.
• The new auto-mode-alist thingy is from Eli, and I'd rather not talk about it.

You also might be interested to hear that we/they added forward/backward sexp navigation, with some further additions planned. But that's only in the master branch.

More detailed history here: https://github.com/emacs-mirror/emacs/commits/master/lisp/progmodes/ruby-ts-mode.el