While looking at the docs for pg_upgrade I noticed some stuff that the
following patch attempts to at least partly address.
There is quite some confusion going on between using "Postgres" and
PostgreSQL, I changed that to the later because that is how we spell the
productname in all the other parts of the docs, also added some further
markups and crossreferences to other docs.
Stuff that seems to need further work is more or less the "limitations"
section, I don't think there are only issues when upgrade from 8.3 but
also from 8.4 (though not as much iirc) there is also the rather bold
"we will support upgrades from every snapshot and alpha release" which
seems very optimistic...
Stefan