* lib/mbmemcasecoll.c: Include <uchar.h> instead of <wctype.h>.
(apply_c32tolower): Renamed from apply_towlower. Use mbrtoc32 instead of
mbrtowc. Use c32tolower instead of towlower. Use c32rtomb instead of
wcrtomb.
* modules/mbmemcasecoll (Depends-on): Remove mbrtowc, wcrtomb. Add
uchar, mbrtoc32, c32rtomb, c32tolower.
(Link): Add $(LIBUNISTRING) $(LIBC32CONV).
* modules/mbmemcasecoll-tests (Makefile.am): Link test-mbmemcasecoll
with $(LIBUNISTRING) $(LIBC32CONV).