* lib/localeinfo.h: Include <uchar.h>. Add special definitions for GAWK.
(case_folded_counterparts): Change array element type to char32_t.
* lib/localeinfo.c: Include <uchar.h>. Add special definitions for GAWK.
(is_using_utf8, init_localeinfo): Use mbrtoc32 instead of mbrtowc.
(lonesome_lower): Change element type to 'unsigned short'.
(case_folded_counterparts): Change array element type to char32_t. Use
c32toupper instead of towupper. Use c32tolower instead of towlower.
* lib/dfa.c: Include <uchar.h>. Add special definitions for GAWK.
(struct mb_char_classes): Change element type of 'chars' to char32_t.
(mbs_to_wchar): Use mbrtoc32 instead of mbrtowc.
(setbit_wc): Change type of first argument to char32_t. Use c32tob
instead of wctob.
(parse_bracket_exp): Update.
(lex): Use c32isprint instead of iswprint. Use c32isspace instead of
iswspace. Use c32rtomb instead of a %lc directive.
(addtok_wc): Use c32rtomb instead of wcrtomb.
(atom): Update.
* modules/dfa (Depends-on): Remove wctype-h. Add uchar, mbrtoc32,
c32rtomb, c32tob, c32tolower, c32toupper, c32isprint, c32isspace.
(Link): Add $(LIBUNISTRING) $(LIBC32CONV).
* modules/dfa-tests (Makefile.am): Link test-dfa-match-aux with
$(LIBUNISTRING) $(LIBC32CONV).
* NEWS: Mention the change.