Log Message:
Changes 8.1.16:
* Fix crash in autovacuum
  The crash occurs only after vacuuming a whole database for
  anti-transaction-wraparound purposes, which means that it occurs
  infrequently and is hard to track down.
* Improve handling of URLs in headline() function
* Improve handling of overlength headlines in headline() function
* Prevent possible Assert failure or misconversion if an encoding
  conversion is created with the wrong conversion function for the
  specified pair of encodings
* Avoid unnecessary locking of small tables in "VACUUM"
* Ensure that the contents of a holdable cursor don't depend on the
  contents of TOAST tables
* Fix uninitialized variables in "contrib/tsearch2"'s get_covers()
  function
* Fix configure script to properly report failure when unable to
  obtain linkage information for PL/Perl
* Make all documentation reference pgsql-bugs and/or pgsql-hackers as
  appropriate, instead of the now-decommissioned pgsql-ports and
  pgsql-patches mailing lists
* Update time zone data files to tzdata release 2009a (for Kathmandu
  and historical DST corrections in Switzerland, Cuba)