WeakRef updated to support Tango, too

[Bill Baxter]

Bill Baxter wrote:
> Tomas Lindquist Olsen wrote:
>> Minor issue, the 'string' alias should be private, or it may conflict 
>> with aliases made by the user.
> 
> As far as I know, private aliases conflict just like public ones, not so?

Bugs that look relevant:
http://d.puremagic.com/issues/show_bug.cgi?id=463
http://d.puremagic.com/issues/show_bug.cgi?id=1161
http://d.puremagic.com/issues/show_bug.cgi?id=1238
http://d.puremagic.com/issues/show_bug.cgi?id=1441

--bb