respsect array and object length requests

mcode.cm

@@ -1930,7 +1930,7 @@ var mcode = function(ast) {
         _i = _i + 1
       }
       dest = alloc_slot()
-      add_instr(["array", dest, 0])
+      add_instr(["array", dest, count])
       _i = 0
       while (_i < count) {
         emit_2("push", dest, elem_slots[_i])
@@ -1943,7 +1943,7 @@ var mcode = function(ast) {
     if (kind == "record") {
       list = expr.list
       dest = alloc_slot()
-      push(s_instructions, ["record", dest, 0])
+      push(s_instructions, ["record", dest, length(list)])
       _i = 0
       while (_i < length(list)) {
         pair = list[_i]