Let genunicodetables determine which files it needs from the unicode
directory.  cmake just needs to pass the directory and destination file
to the script.

Problem:    Handling emoji characters as full width has problems with
            backwards compatibility.
Solution:   Only put characters in the 1f000 range in the emoji table.

https://github.com/vim/vim/commit/6a08454b93784c92296d4c08456401cbaa74c9d5

Problem:    Handling emoji characters as full width has problems with
            backwards compatibility.
Solution:   Remove ambiguous and double width characters from the emoji table.
            Use a separate table for the character class.
            (partly by Yashuhiro Matsumoto)

https://github.com/vim/vim/commit/b86f10ee10bdf932df02bdaf601dffa671518a47

Problem:    Emoji characters are not considered as a kind of word character.
Solution:   Give emoji characters a word class number. (Yashuhiro Matsumoto)

https://github.com/vim/vim/commit/4077b33a8370afb3d5ae74e556a0119cf51fe294

Problem:    Although emoji characters are ambiguous width, best is to treat
            them as full width.
Solution:   Update the Unicode character tables. Add the 'emoji' options.
            (Yasuhiro Matsumoto)

https://github.com/vim/vim/commit/3848e00e0177abdb31bc600234967863ec487233