New implementation of <original-package> tag.

We now have the new package retain the name of the old package.  This makes
sure that all existing references to it (shortcuts, widgets, etc) will still
work.

This does mean that your package can run under either the old or new name,
depending on whether the user got it with an update.  Buyer beware!

I have tried testing all of the paths of updating, installing another
update in /data, uninstalling the update, updating system with an even
newer update, etc.  I think they all work.  No promises though.