This allows us to:
- perform scatter gather operations without using temporary files,
- create non-linear pipelines, and
- implement file views using symbolic links.
File view idea by: Vassilios Karakoidas
Portalfs pointer by: John Ioannidis
MFC after: 1 month
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
