Problem:
As checkhealth grows, it is increasingly hard to quickly glance through
the information.

Solution:
Show a summary of ok, warn, and error outputs per section.

Problem:  Using wrong window in ll_resize_stack()
          (after v9.1.1287)
Solution: Use "wp" instead of "curwin", even though they are always the
          same value.  Fix typos in documentation (zeertzjq).

closes: vim/vim#17080

https://github.com/vim/vim/commit/b71f1309a210bf8f61a24f4eda336de64c6f0a07

Problem:  quickfix and location-list stack is limited to 10 items
Solution: add the 'chistory' and 'lhistory' options to configure a
          larger quickfix/location list stack
          (64-bitman)

closes: vim/vim#16920

https://github.com/vim/vim/commit/88d41ab270a8390a43da97a903b1a4d76b89d330

Co-authored-by: 64-bitman <60551350+64-bitman@users.noreply.github.com>
Co-authored-by: Hirohito Higashi <h.east.727@gmail.com>

Problem:
`client_is_stopped(…)` is an alias for `not get_client_by_id(…)`.
And it's not used anywhere in our codebase.

Solution:
Deprecate it.

Problem:  inline word diff treats multibyte chars as word char
          (after 9.1.1243)
Solution: treat all non-alphanumeric characters as non-word characters
          (Yee Cheng Chin)

Previously inline word diff simply used Vim's definition of keyword to
determine what is a word, which leads to multi-byte character classes
such as emojis and CJK (Chinese/Japanese/Korean) characters all
classifying as word characters, leading to entire sentences being
grouped as a single word which does not provide meaningful information
in a diff highlight.

Fix this by treating all non-alphanumeric characters (with class number
above 2) as non-word characters, as there is usually no benefit in using
word diff on them. These include CJK characters, emojis, and also
subscript/superscript numbers. Meanwhile, multi-byte characters like
Cyrillic and Greek letters will still continue to considered as words.

Note that this is slightly inconsistent with how words are defined
elsewhere, as Vim usually considers any character with class >=2 to be
a "word".

related: vim/vim#16881 (diff inline highlight)
closes: vim/vim#17050

https://github.com/vim/vim/commit/9aa120f7ada592ed03b37f4de8ee413c5385f123

Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>

closes: vim/vim#17036

https://github.com/vim/vim/commit/b8d5c8509998f3a97ffe42f674352b07749cd119

Co-authored-by: Christian Brabandt <cb@256bit.org>

It's not used anywhere.

Problem:
First rtp directory is unpredictable and not in line with XDG
base spec.

Solution:
Use stdpath('data')/spell as directory if 'spellfile' is not set.

Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Co-authored-by: Justin M. Keyes <justinkz@gmail.com>

Problem: `severity` field is recognized by
  `vim.diagnostic.Opts.VirtualLines`, but it is not explicitly
  documented.

Solution: document it.