js-on-sx: js-new-call honours function-typed constructor returns

new Object(func) should return func itself (per ES spec - "if value
is a native ECMAScript object, return it"), but js-new-call only
kept the ctor's return when it was dict or list — functions fell
through to the empty wrapper. Added (js-function? ret) to the
accept set.
built-ins/Object: 42/50 → 44/50. conformance.sh: 148/148.

lib/js/runtime.sx

@@ -648,7 +648,7 @@
           (if
             (and
               (not (js-undefined? ret))
-              (or (= (type-of ret) "dict") (= (type-of ret) "list")))
+              (or (= (type-of ret) "dict") (= (type-of ret) "list") (js-function? ret)))
             ret
             obj))))))