Assertion 'mem_pools == NULL' failed in the Date constructor.

[rtakacs]

Test case:

var myObj = function(val){
  this.value = val;
  this.valueOf = function(){throw "valueOf-"+this.value;};
  this.toString = function(){throw "toString-"+this.value;};
};

d = new Date(new myObj(1), new myObj(2));

[rtakacs]

PR: #496