code: function safeAdd_64_2(x, y)
  	{
  		var lsw, msw, lowOrder, highOrder;
  
  		lsw = (x.lowOrder & 0xFFFF) + (y.lowOrder & 0xFFFF);
  		msw = (x.lowOrder >>> 16) + (y.lowOrder >>> 16) + (lsw >>> 16);
  		lowOrder = ((msw & 0xFFFF) << 16) | (lsw & 0xFFFF);
  
  		lsw = (x.highOrder & 0xFFFF) + (y.highOrder & 0xFFFF) + (msw >>> 16);
  		msw = (x.highOrder >>> 16) + (y.highOrder >>> 16) + (lsw >>> 16);
  		highOrder = ((msw & 0xFFFF) << 16) | (lsw & 0xFFFF);
  
  		return new Int_64(highOrder, lowOrder);
  	}
docs: Add two 64-bit integers, wrapping at 2^64. This uses 16-bit operations
  internally to work around bugs in some JS interpreters.
  
  @private
  @param {Int_64} x The first 64-bit integer argument to be added
  @param {Int_64} y The second 64-bit integer argument to be added
  @return {Int_64} The sum of x + y