The AC_CHECK_FUNCS has the following synopsis:
AC_CHECK_FUNCS(function..., [action-if-found], [action-if-not-found]).
Fourth argument doesn't exist.
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AC_CHECK_HEADERS([wchar.h])
-AC_CHECK_FUNCS([mblen])
-AC_CHECK_FUNCS([mbrlen mbsinit],,,[
-#ifdef HAVE_WCHAR_H
-# include <wchar.h>
-#endif
-])
+AC_CHECK_FUNCS([mblen mbrlen mbsinit])
AC_CACHE_CHECK([for mbstate_t], [ac_cv_type_mbstate_t],[
AC_TRY_COMPILE([
#ifdef HAVE_WCHAR_H