fix nl_langinfo_l(CODESET, loc) reporting wrong locale's value

use of MB_CUR_MAX encoded a hidden dependency on the currently active
locale for the calling thread, whereas nl_langinfo_l is supposed to
report for the locale passed as an argument.

src/locale/langinfo.c

@@ -33,7 +33,7 @@ char *__nl_langinfo_l(nl_item item, locale_t loc)
 	int idx = item & 65535;
 	const char *str;
 
-	if (item == CODESET) return MB_CUR_MAX==1 ? "ASCII" : "UTF-8";
+	if (item == CODESET) return loc->cat[LC_CTYPE] ? "UTF-8" : "ASCII";
 
 	/* _NL_LOCALE_NAME extension */
 	if (idx == 65535 && cat < LC_ALL)