runtime(vim): Update base-syntax, fix escaping :syn and :hi sub-groups (#14137)

* runtime(vim): Update base-syntax, fix escaping :syn and :hi sub-groups

- Remove contained :syntax and :highlight sub-groups from the function
  body cluster.  These should only match in the respective commands.
- Remove vimSynLine syntax group from several clusters.  The definition
  of vimSynLine was removed in Vim 5.3.

* runtime(vim): Update syntax generator, use standard Last Change date format

The de facto standard date format is YYYY MMM DD.

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/generator/update_date.vim

@@ -7,7 +7,7 @@ normal gg
 let pat = '^"\s*Last\s*Change:\s\+'
 let lnum = search(pat, 'We', 10)
 if lnum > 0
-   exec 'norm! lD"=strftime("%b %d, %Y")' . "\rp"
+   exec 'norm! lD"=strftime("%Y %b %d")' . "\rp"
    silent update
 endif
 quitall!