Fix crash in autovacuum (Alvaro)

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 (Teodor)

Improve handling of overlength headlines in headline() function (Teodor)

Prevent possible Assert failure or misconversion if an encoding conversion is created with the wrong conversion function for the specified pair of encodings (Tom, Heikki)

Avoid unnecessary locking of small tables in VACUUM (Heikki)

Ensure that the contents of a holdable cursor don't depend on the contents of TOAST tables (Tom)

Previously, large field values in a cursor result might be represented as TOAST pointers, which would fail if the referenced table got dropped before the cursor is read, or if the large value is deleted and then vacuumed away. This cannot happen with an ordinary cursor, but it could with a cursor that is held past its creating transaction.

Fix uninitialized variables in contrib/tsearch2's get_covers() function (Teodor)

Fix configure script to properly report failure when unable to obtain linkage information for PL/Perl (Andrew)

Make all documentation reference pgsql-bugs and/or pgsql-hackers as appropriate, instead of the now-decommissioned pgsql-ports and pgsql-patches mailing lists (Tom)

Update time zone data files to tzdata release 2009a (for Kathmandu and historical DST corrections in Switzerland, Cuba)