Word boundaries are based on whether a character is alphanumeric or
not. For the PG_UNICODE_FAST collation, alphanumeric includes
non-ASCII digits; whereas for the PG_C_UTF8 collation, it only
includes digits 0-9. Pass down the right information from the
pg_locale_t into initcap_wbnext to differentiate the behavior.
Reported-by: Noah Misch <noah@leadboat.com>
Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/20250417135841.33.nmisch@google.com
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