Speed-up !SubversionNode.get_entries() by nearly a factor 100.
Apparently, it's quite costly to call `fs.revision_root`, so re-using the one from the parent node is a huge win (the `rev` of that revision root is guaranteed to be the same).
Related to #5782.
Authored by: cboos 2008-04-01
Parent: [r6786]
Child: [r6788]
