xgettext: Improve JSX support in JavaScript.

xgettext: Improve JSX support in JavaScript.

Reported by Vaclav Slavik <vaclav@slavik.io> in
<https://savannah.gnu.org/bugs/?57927>.

* gettext-tools/src/x-javascript.c (enum token_type_ty): Add some more types.
(is_after_expression): New function.
(phase5_get): Distinguish the "other" tokens in more detail. Use
'is_after_expression ()' when interpreting a '<' or '/' character.
(extract_balanced): Don't let commas in braced expressions and in XML elements
disturb the argument processing outside.
(extract_javascript): Update.
* gettext-tools/tests/xgettext-javascript-6: Enhance the test.
* NEWS: Mention the change.