Now `:InspectTree` will show missing nodes as e.g. `(MISSING identifier)`
or `(MISSING ";")` rather than just `(identifier)` or `";"`. This is
doable because the `MISSING` keyword is now valid query syntax.

Co-authored-by: Christian Clason <c.clason@uni-graz.at>

Problem:  vim_strnchr() is strange and unnecessary (after v9.1.1009)
Solution: Remove vim_strnchr() and use memchr() instead.  Also remove a
          comment referencing an #if that is no longer present.

vim_strnchr() is strange in several ways:
- It's named like vim_strchr(), but unlike vim_strchr() it doesn't
  support finding a multibyte char.
- Its logic is similar to vim_strbyte(), but unlike vim_strbyte() it
  uses char instead of char_u.
- It takes a pointer as its size argument, which isn't convenient for
  all its callers.
- It allows embedded NULs, unlike other "strn*" functions which stop
  when encountering a NUL byte.

In comparison, memchr() also allows embedded NULs, and it converts bytes
in the string to (unsigned char).

closes: vim/vim#16579

https://github.com/vim/vim/commit/34e1e8de91ff4a8922d454e3147ea425784aa0a0

and sync queries from nvim-treesitter (adds support for `MISSING` nodes).

Problem:  diff feature can be improved
Solution: include the linematch diff alignment algorithm
          (Jonathon)

closes: vim/vim#9661

https://github.com/vim/vim/commit/7c7a4e6d1ad50d5b25b42aa2d5a33a8d04a4cc8a

Co-authored-by: Jonathon <jonathonwhite@protonmail.com>

Problem:  SpotBugs compiler can be further improved
Solution: Introduce event-driven primitives for SpotBugs
          (Aliaksei Budavei)

closes: vim/vim#16258

https://github.com/vim/vim/commit/2e252474c4df5018b9819d86ebb70bf3b1b1a1af

Co-authored-by: Aliaksei Budavei <0x000c70@gmail.com>

Problem:  SpotBugs compiler can be improved
Solution: runtime(compiler): Improve defaults and error handling for
          SpotBugs; update test_compiler.vim (Aliaksei Budavei)

runtime(compiler): Improve defaults and error handling for SpotBugs

* Keep "spotbugs#DefaultPreCompilerTestAction()" defined but
  do not assign its Funcref to the "PreCompilerTestAction"
  key of "g:spotbugs_properties": there are no default and
  there can only be introduced arbitrary "*sourceDirPath"
  entries; therefore, this assignment is confusing at best,
  given that the function's implementation delegates to
  whatever "PreCompilerAction" is.

* Allow for the possibility of relative source pathnames
  passed as arguments to Vim for the Javac default actions,
  and the necessity to have them properly reconciled when
  the current working directory is changed.

* Do not expect users to remember or know that new source
  files ‘must be’ ":argadd"'d to be then known to the Javac
  default actions; so collect the names of Java-file buffers
  and Java-file Vim arguments; and let users providing the
  "@sources" file-lists in the "g:javac_makeprg_params"
  variable update these file-lists themselves.

* Strive to not leave behind a fire-once Syntax ":autocmd"
  for a Java buffer whenever an arbitrary pre-compile action
  errors out.

* Only attempt to run a post-compiler action in the absence
  of failures for a pre-compiler action.  Note that warnings
  and failures are treated alike (?!) by the Javac compiler,
  so when previews are tried out with "--enable-preview",
  remember about passing "-Xlint:-preview" too to also let
  SpotBugs have a go.

* Properly group conditional operators when testing for key
  entries in a user-defined variable.

* Also test whether "javaExternal" is defined when choosing
  an implementation for source-file parsing.

* Two commands are provided to toggle actions for buffer-local
  autocommands:
  - SpotBugsRemoveBufferAutocmd;
  - SpotBugsDefineBufferAutocmd.

For example, try this from "~/.vim/after/ftplugin/java.vim":
------------------------------------------------------------
if exists(':SpotBugsDefineBufferAutocmd') == 2
	SpotBugsDefineBufferAutocmd BufWritePost SigUSR1
endif
------------------------------------------------------------

And ":doautocmd java_spotbugs User" can be manually used at will.

closes: vim/vim#16140

https://github.com/vim/vim/commit/368ef5a48c7a41af7fe2c32a5d5659e23aff63d0

Co-authored-by: Aliaksei Budavei <0x000c70@gmail.com>