BUG #8680: Fix initialization of pg_clog and pg_subtrans during hot standby startup

The following bug has been logged on the website:

Bug reference:      8680
Logged by:          Martin von Oertzen
Email address:      launchpad@maletin.de
PostgreSQL version: 9.2.4
Operating system:   ubuntu 12.04.3 LTS
Description:

A table has a primary key.
We use pg_basebackup to start a
streaming replication server.
after a trigger, this standby is
used as master and the primary key
is shown as valid and there are no
duplicates.


alter table t add column c int4 not null default 0;
FEHLER:  konnte Unique Index »t_pkey« nicht erstellen
DETAIL:  Schlüssel (username, authority)=(malu001, ROLE_STEUER) ist doppelt
vorhanden.


It looks like a bug that is fixed in
9.2.6, but i can't believe, that this
bug was introduced in 9.2.5, because we
can reproduce this with 9.2.4.
But only with massive work while the
basebackup is in progress.