PCRE2 has a bug when using PCRE2_MATCH_INVALID_UTF: it would
sometimes fail to match patterns using negative classes
like \W and \D.
* NEWS (Bug fixes): Mention it.
* src/pcre2search.c: Restrict impact of the bug.
Do not use the problematic flag with broken versions of PCRE2.
Also, generate locale tables only for single-byte locales,
as the PCRE2 documentation recommends this.
* tests/Makefile.am (TESTS): Add the file name
* tests/pcre-utf8-bug224: New file, to test for this.