Note: currently they are both *dumped*, but parsing them produces an error. This
is inappropriate: variables should either be skipped with error message when
dumping or should be read back properly.
It also appears that I did not have test for “has wrong variable value type”
error, so nothing got removed from errors_spec.
- Remove unused variables.
- Do not use helpers.nvim_feed in most cases.
- Do not use helpers.nvim and helpers.nvim_eval at all.
- Add helpers.funcs and helpers.\*meths special tables. Indexing such table
creates functions which call helpers.call or helpers.nvim (and similar) with
first argument equal to table index.
