Problem:
During a refactor long ago, we changed the `getdigits_*` familiy of
functions to abort on overflow.  But this is often wrong, because many
of these codepaths are handling user input.

Solution:
Decide at each call-site whether to use "strict" mode.

fix #5555

Eliminate `expect_err` in favor of `pcall_err` + `eq` or `matches`.

This is better practice in general, and allows to remove the "helptags
ALL" hacks.

Ref: https://github.com/neovim/neovim/issues/8824
Ref: https://github.com/neovim/neovim/commit/f1b67c3453c

* Makefile: fix dependencies with regard to helptags

- use the file as the main target to avoid unnecessary triggering
- use "make oldtest" on Travis to ensure it gets built

For unknown reasons it does not have the trailing space in `:args`
output there anymore:

    [  FAILED  ] test/functional\ex_cmds\arg_spec.lua @ 11: :argument does not restart :terminal buffer
    test/functional\ex_cmds\arg_spec.lua:25: Expected objects to be the same.
    Passed in:
    (string) '
    [term://.//4552:C:\Windows\system32\cmd.exe]'
    Expected:
    (string) '
    [term://.//4552:C:\Windows\system32\cmd.exe] '
    stack traceback:
            test/functional\ex_cmds\arg_spec.lua:25: in function <test/functional\ex_cmds\arg_spec.lua:11>

The test is not about that though, and this can be made less strict by
using `trim()`.  The new test in `test_arglist.vim` for no trailing
newline is OK, and contains trailing spaces.  So this is likely due to
the length of it exceeding the column width already.

The inspect modules is vendored as `vim.inspect`, and therefore it makes
sense to use this in tests also.

Ref: https://github.com/neovim/neovim/issues/6580
Ref: https://github.com/neovim/neovim/commit/bb3aa824b

Use it to improve ls_spec: it should not use the user's real shell for
performance and other reasons.

This matches Vim behavior. From `:help :ls` :

    R    a terminal buffer with a running job
    F    a terminal buffer with a finished job
    ?    a terminal buffer without a job: `:terminal NONE`

TODO: implement `:terminal NONE`.

ref #10349

Problem:    No simple way to label quickfix entries.
Solution:   Add the "module" item, to be used instead of the file name for
            display purposes. (Martin Szamotulski)

https://github.com/vim/vim/commit/d76ce852668635d81778cedacc2d3f021ed4e475