Google seems to have finally updated its documentation for sub-domain & cross-domain tracking. [code.google.com ]
The _setAllowHash() object method has been deprecated [code.google.com ].This method reduces the domain hash value to an arbitrary number (usually ‘1’) so that cookies from other tracked domains do not get rejected. It was never required for sub-domain tracking to work; but Google’s earlier documentation had, quite redundantly, included this.
Another change is that the leading period in the _setDomainName() method has been removed i.e. the preferred method to define the domain name is
Not sure why this change has been brought into the picture.
In any case, I don't think it would be wise to go ahead & change the current tracking codes according to the newly introduced revisions in the documentation. It could screw up the returning visitors metric.