Log Message:
Changes 8.1.7:
* Remove security vulnerabilities that allowed connected users to
  read backend memory
* Fix rare bug wherein btree index page splits could fail due to
  choosing an infeasible split point
* Improve "VACUUM" performance for databases with many tables
* Fix autovacuum to avoid leaving non-permanent transaction IDs in
  non-connectable databases
  This bug affects the 8.1 branch only.
* Fix for rare Assert() crash triggered by UNION
* Tighten security of multi-byte character processing for UTF8
  sequences over three bytes long
* Fix bogus "permission denied" failures occurring on Windows due to
  attempts to fsync already-deleted files
* Fix possible crashes when an already-in-use PL/pgSQL function is
  updated