dojo._Url broken for more than two args

[Mike Wilson]

Two args ok:

new dojo._Url("http://mysite.com/a/b/c/d.html", "..")
-> http://mysite.com/a/b/

Three args broken:

new dojo._Url("http://mysite.com/a/b/c/d.html", "..", "..")
-> ..

The reason seems to be the local variable first initialized as:

var uri = [_a[0]];

and then used in a different way later on, thereby corrupting state after the first iteration in the arguments loop.

[Adam Peller]

dup of #7935