o  use version-specific tablespace directory names so renaming mount points does not fail
o  remove copy_dir code, or use it
o  handle large object comments;  this is difficult to do because the large object
   doesn't exist when --schema-only is loaded
o  consider using pg_depend for checking object usage in version.c
o  add --delete-old option to delete old cluster files
o  if reindex is necessary, allow it to be done in parallel with pg_dump custom format
o  support migration from Postgres 8.2 to 8.4?
