Convert src/mbyte.c to ANSI functions.

It was a false positive, but it can't hurt to "fix" it.

Original warning:
CID 13685 (#1 of 1): Buffer not null terminated (BUFFER_SIZE)
6. buffer_size: Calling strncpy with a source string whose length (4 chars)
is greater than or equal to the size argument (4) will fail to
null-terminate b0p->b0_version.

It was a false positive, but it can't hurt to "fix" it.

Original warning:
CID 13685 (#1 of 1): Buffer not null terminated (BUFFER_SIZE)
6. buffer_size: Calling strncpy with a source string whose length (4 chars)
is greater than or equal to the size argument (4) will fail to
null-terminate b0p->b0_version.

It was a false positive, but it can't hurt to "fix" it.

Original warning:
CID 13685 (#1 of 1): Buffer not null terminated (BUFFER_SIZE)
6. buffer_size: Calling strncpy with a source string whose length (4 chars)
is greater than or equal to the size argument (4) will fail to
null-terminate b0p->b0_version.

It was a false positive, but it can't hurt to "fix" it.

Original warning:
CID 13685 (#1 of 1): Buffer not null terminated (BUFFER_SIZE)
6. buffer_size: Calling strncpy with a source string whose length (4 chars)
is greater than or equal to the size argument (4) will fail to
null-terminate b0p->b0_version.

It was a false positive, but it can't hurt to "fix" it.

Original warning:
CID 13685 (#1 of 1): Buffer not null terminated (BUFFER_SIZE)
6. buffer_size: Calling strncpy with a source string whose length (4 chars)
is greater than or equal to the size argument (4) will fail to
null-terminate b0p->b0_version.

It was a false positive, but it can't hurt to "fix" it.

Original warning:
CID 13685 (#1 of 1): Buffer not null terminated (BUFFER_SIZE)
6. buffer_size: Calling strncpy with a source string whose length (4 chars)
is greater than or equal to the size argument (4) will fail to
null-terminate b0p->b0_version.

It was a false positive, but it can't hurt to "fix" it.

Original warning:
CID 13685 (#1 of 1): Buffer not null terminated (BUFFER_SIZE)
6. buffer_size: Calling strncpy with a source string whose length (4 chars)
is greater than or equal to the size argument (4) will fail to
null-terminate b0p->b0_version.

It was a false positive, but it can't hurt to "fix" it.

Original warning:
CID 13685 (#1 of 1): Buffer not null terminated (BUFFER_SIZE)
6. buffer_size: Calling strncpy with a source string whose length (4 chars)
is greater than or equal to the size argument (4) will fail to
null-terminate b0p->b0_version.

Syncing

A lot of code inside HAVE_WORKING_LIBINTL doesn't really depend on a
"working libintl". For instance ex_language is also used for ":lang collate"
and ":lang time".

Also ":lang C" should not fail just because translations aren't available (it
just means use the default text).

References:

neovim#1 2d00ead
separate ifdefs for locale and gettext got merged together.

neovim@8253e29
Unmotivated switcharoo of get_mess_env() logic. If available, get_locale_val(LC_MESSAGES) is the correct implementation.

(cherry picked from commit 3a44db5)

…ders #31608

Problem:
regression since #31340

`nvim -l repro.lua`:
```lua
vim.lsp.start { cmd = { 'lua-language-server' }, name = 'lua_ls' }
vim.lsp.start { cmd = { 'lua-language-server' }, name = 'lua_ls', root_dir = 'foo' }

-- swapped case will be ok:
-- vim.lsp.start { cmd = { 'lua-language-server' }, name = 'lua_ls', root_dir = 'foo' }
-- vim.lsp.start { cmd = { 'lua-language-server' }, name = 'lua_ls' }
```

Failure:
```
E5113: Error while calling lua chunk: /…/lua/vim/lsp.lua:214: bad argument #1 to
'ipairs' (table expected, got nil)
stack traceback:
        [C]: in function 'ipairs'
        /…/lua/vim/lsp.lua:214: in function 'reuse_client'
        /…/lua/vim/lsp.lua:629: in function 'start'
        repro.lua:34: in main chunk
```

this change includes the following changes:
- a macro option must be #1–#9
- add \providecommand
- add starred versions of \newcommand, \newenvironment, and their
  variants
- add number of arguments to \(re)newenvironment

vim/vim@a35040f

Co-authored-by: Eisuke Kawashima <[email protected]>

Problem:
Bad format() call on PUC Lua #34901

    Error: Failed to run healthcheck for "vim.health" plugin. Exception:
    runtime/lua/vim/health/health.lua:89: bad argument #1 to 'format' (string expected, got nil)

Solution:
Avoid passing nil.

Problem:
Bad format() call on PUC Lua #34901

    Error: Failed to run healthcheck for "vim.health" plugin. Exception:
    runtime/lua/vim/health/health.lua:89: bad argument #1 to 'format' (string expected, got nil)

Solution:
Avoid passing nil.

(cherry picked from commit 2422fbd)

Problem:
Bad format() call on PUC Lua

    Error: Failed to run healthcheck for "vim.health" plugin. Exception:
    runtime/lua/vim/health/health.lua:89: bad argument #1 to 'format' (string expected, got nil)

Solution:
Avoid passing nil.

(cherry picked from commit 2422fbd)

Co-authored-by: Justin M. Keyes <[email protected]>

Problem:
The "gitsigns" plugin runs `vim.diff` in a thread (`uv.new_work`), but
`vim.diff` is nil in that context:

    Lua callback:
    …/gitsigns.nvim/lua/gitsigns/diff_int.lua:30: bad argument #1 to 'decode' (string expected, got nil)
    stack traceback:
      [C]: in function 'decode'
      …/gitsigns.nvim/lua/gitsigns/diff_int.lua:30: in function <…/gitsigns.nvim/lua/gitsigns/diff_int.lua:29>
    Luv thread:
    …/gitsigns.nvim/lua/gitsigns/diff_int.lua:63: attempt to call field 'diff' (a nil value)

Solution:
Revert the `stdlib.c` change (set `vim.diff` instead of `vim._diff`).

`scrolloff`, `conceallevel`, and `modeline` all get disabled by default.

Closes: neovim#1