* Add docs about lua-prefix-key machinery
* Support line-continuation with commas, e.g.
   x,y = long_value,
         other_long_value

* Support line-continuation commas in `for ... do ' operators
* Fix braces/parens that reduce indent by const offset
   this causes wrong behavior when indented block was
   anchored to first line, e.g.
   my_func( hello,
            world
         )

* Redo syntax engine using semantic/wisent
