Behavior of `config_setting_lookup_*` is inconsistent with `config_setting_lookup`

[yshui]

For example config_setting_lookup_int does not call config_setting_lookup but instead calls config_setting_get_member, which unlike config_setting_lookup, requires the setting to be a group, and doesn't support indexing ([0]).

This is surprising. From the function name, one would expect config_setting_lookup_int to be the same as config_setting_get_int(config_setting_lookup()).

[hyperrealm]

This inconsistency is unfortunate but changing the behavior now would break a lot of existing code, so I don't think we should do it.