Updated libconfig to version 1.4.9

Previous edits to the library have been preserved with this update. No
functional changes, other than some edge-case fixes (see libconfig
changelog). In case of issues, please let me know / file a bugreport.

Signed-off-by: Haru <haru@dotalux.com>
Re-generated libconfig parser and scanner

This overrides previous manual edits to the machine-generated files, and
is supposed to make it much easier to maintain in future.

There should be no functional changes at all, but if there's any issue,
please let me know.

Signed-off-by: Haru <haru@dotalux.com>