- json: sorted class fields (#2)

    - change ordered search threshold from 8 to 4

src/cxon/lang/common/cio/class.hxx

@@ -233,7 +233,7 @@ namespace cxon { namespace cio { namespace cls {
 
         template <typename X, typename T, typename ...Fs, typename II, typename Cx>
             constexpr bool read_field_(T& t, const char* name, const fields_for_read<T, Fs...>& fs, int (&st)[sizeof...(Fs)], II& i, II e, Cx& cx) {
-                return fs.ordered && sizeof...(Fs) > 8 ?
+                return fs.ordered && sizeof...(Fs) > 4 ?
                     read_ordered_  <X, 0, sizeof...(Fs) - 1>::field(t, name, fs, st, i, e, cx) :
                     read_unordered_<X, 0, sizeof...(Fs)    >::field(t, name, fs, st, i, e, cx)
                 ;