Fix localedata test builds with latest GCC

	* localedata/Makefile (CFLAGS-tst_iswalnum.c, CFLAGS-tst_iswalpha.c
	CFLAGS-tst_iswcntrl.c, CFLAGS-tst_iswdigit.c, CFLAGS-tst_iswgraph.c,
	CFLAGS-tst_iswlower.c, CFLAGS-tst_iswprint.c, CFLAGS-tst_iswpunct.c,
	CFLAGS-tst_iswspace.c, CFLAGS-tst_iswupper.c, CFLAGS-tst_iswxdigit.c,
	CFLAGS-tst_towlower.c, CFLAGS-tst_towupper.c): New macros.