mb_isupper
  vim_tolower vim_toupper                          mb_tolower mb_toupper
  mb_ptr2len                                           utfc_ptr2len
  mb_ptr2len_len                                     utfc_ptr2len_len
  mb_char2len                                          utf_char2len
  mb_char2bytes                                       utf_char2bytes
  mb_ptr2cells                                         utf_ptr2cells
  mb_ptr2cells_len                                   utf_ptr2cells_len
  mb_char2cells                                       utf_char2cells
  mb_off2cells                                         utf_off2cells
  mb_ptr2char                                          utf_ptr2char
  mb_head_off                                          utf_head_off
  mb_tail_off                                          utf_cp_bounds
  mb_strnicmp2                                         utf_strnicmp
  MB_STRNICMP2                                         utf_strnicmp
  mb_lefthalve                                        grid_lefthalve
  mb_fix_col                                           grid_fix_col
  utf_off2cells                                       grid_off2cells
  ml_get_curline                                    get_cursor_line_ptr
  ml_get_cursor                                     get_cursor_pos_ptr
  ml_get_curline_len                                get_cursor_line_len
  ml_get_cursor_len                                 get_cursor_pos_len
  screen_char                                             ui_line
  screen_line                                        grid_put_linebuf
  screen_* (most functions)                               grid_*
  update_prepare, update_finish #9484                  removed; use update_screen only
  ARRAY_LENGTH                                          ARRAY_SIZE
  vim_strsave_escape_csi                           vim_strsave_escape_ks
  vim_unescape_csi                                    vim_unescape_ks
  gettail                                                path_tail
  mch_isFullName                                     path_is_absolute
  script_do_profile                                    profile_init

  -----------------------------------------------------------------------
<
Make sure to note the difference between `utf_` and `utfc_` when replacing
`mb_` functions. Also indirect call syntax `(*mb_ptr2len)(...)` should be
replaced with an ordinary function call `utfc_ptr2len(...)`.
>
  -----------------------------------------------------------------------
  Data type    Format (Vim source)     Portable format (Nvim source)
  ------------ ----------------------- ----------------------------------
  long long    "%lld"                  "%" PRId64
  size_t       "%ld"                   "%zu"
  linenr_T     "%ld"                   "%" PRIdLINENR
  -----------------------------------------------------------------------
<
- See also: https://github.com/neovim/neovim/pull/1729#discussion_r22423779
- Vim's `ga_init2` was renamed to `ga_init` and the original `ga_init` is
  gone.
- "Old style" Vim tests (`src/testdir/*.in`) should be converted to Lua tests
  (see #1286 https://github.com/neovim/neovim/issues/1286 and #1328
  https://github.com/neovim/neovim/pull/1328). See Checklist for migrating
  legacy tests
  https://github.com/neovim/neovim/blob/master/test/README.md#checklist-for-migrating-legacy-tests.
    - However, please do not convert "new style" Vim tests
      (`src/testdir/*.vim`) to Lua. The "new style" Vim tests are faster than
      the old ones, and converting them takes time and effort better spent
      elsewhere. Just copy them to `test/old/testdir/*.vim`.
- Conditions that check `enc_utf8` or `has_mbyte` are obsolete (only the
  "true" case is applicable).
    - `enc_utf8` and `has_mbyte` macros were removed in
      https://github.com/neovim/neovim/pull/13293
- Check for `CSI` in typeahead buffer is only necessary in Vim with
  `FEAT_GUI`. `CSI` does not have a special meaning