Some (poorly-implemented) LSPs can return an empty JSON object in
LSP responses, which could cause tokens to be nil, which would eventually
cause an error and a bad UI experience. This fix makes sure that the
tokens variable is always set to a non-nil value.

Problem:    Cannot lock a variable in legacy Vim script like in Vim9.
Solution:   Make ":lockvar 0" work.

https://github.com/vim/vim/commit/a187c43cfe8863d48b2159d695fedcb71f8525c1

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:    Cannot read back what setcellwidths() has done.
Solution:   Add getcellwidths(). (Kota Kato, closes vim/vim#11837)

https://github.com/vim/vim/commit/66bb9ae70f7371456ed76518076d2a344f8ab417

Co-authored-by: Kota Kato <github@kat0h.com>

- also unset b:ts_highlight on stop()

Fixes: #21836

Problem:    No completion for :scriptnames.
Solution:   Implement :scriptnames completion. (Yegappan Lakshmanan,
            closes vim/vim#10005)

https://github.com/vim/vim/commit/454ce6737cadb82886f1fc0eb9e8666cc59ae42b

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Problem:    No fuzzy cmdline completion for user defined completion.
Solution:   Add fuzzy completion for user defined completion. (Yegappan
            Lakshmanan, closes vim/vim#9858)

https://github.com/vim/vim/commit/afd4ae35d66b2e7732eceb5ad9f6b4ece6b7c64c

Cherry-pick related docs from Vim runtime.

N/A patches for version.c:

vim-patch:8.2.4485: compiler warning for uninitialized variable
vim-patch:8.2.4732: duplicate code to free fuzzy matches

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Problem:    getcompletion() does not work properly when 'wildoptions
            contains "fuzzy".
Solution:   Do not use addstar(). (Yegappan Lakshmanan, closes vim/vim#9992,
            closes vim/vim#9986)

https://github.com/vim/vim/commit/e7dd0fa2c61fe71f12c72b0dcb7bb6415eb048fb

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

Problem:    Completion only uses strict matching.
Solution:   Add the "fuzzy" item for 'wildoptions'. (Yegappan Lakshmanan,
            closes vim/vim#9803)

https://github.com/vim/vim/commit/38b85cb4d7216705058708bacbc25ab90cd61595

Use MAX_FUZZY_MATCHES in fuzzy_match_str().
Omit fuzmatch_str_free() as it is only used on allocation failure.

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

fix(column)!: ensure 'statuscolumn' works with virtual and wrapped lines

BREAKING CHANGE: In 'statuscolumn' evaluation, `v:wrap` has been
replaced by `v:virtnum`. `v:virtnum` is negative when drawing
virtual lines, zero when drawing the actual buffer line, and
positive when drawing the wrapped part of a buffer line.

Problem: On tmux v3.2+, the `terminal-features` option may be used to enable RGB
capabilities over `terminal-overrides`. However, `show-messages` cannot be used
to detect if RGB capabilities are enabled using `terminal-features`.

Solution: Try to use `display-message -p #{client_termfeatures}` instead.
The returned features include "RGB" if either "RGB" is set in
`terminal-features`, or if "Tc" or "RGB" is set in `terminal-overrides` (as
before).
Nothing is returned by tmux versions older than v3.2, so fallback to checking
`show-messages` in that case.

Also, un-Vimscriptify the previous logic a bit, and change the error message to
point to using the `terminal-features` option instead for newer tmux versions.