Fix mishandling of background worker PGPROCs in EXEC_BACKEND builds.

InitProcess() relies on IsBackgroundWorker to decide whether the PGPROC
for a new backend should be taken from ProcGlobal's freeProcs or from
bgworkerFreeProcs.  In EXEC_BACKEND builds, InitProcess() is called
sooner than in non-EXEC_BACKEND builds, and IsBackgroundWorker wasn't
getting initialized soon enough.

Report by Noah Misch.  Diagnosis and fix by me.
Avoid wholesale autovacuuming when autovacuum is nominally off.

When autovacuum is nominally off, we will still launch autovac workers
to vacuum tables that are at risk of XID wraparound.  But after we'd done
that, an autovac worker would proceed to autovacuum every table in the
targeted database, if they meet the usual thresholds for autovacuuming.
This is at best pretty unexpected; at worst it delays response to the
wraparound threat.  Fix it so that if autovacuum is nominally off, we
*only* do forced vacuums and not any other work.

Per gripe from Andrey Zhidenkov.  This has been like this all along,
so back-patch to all supported branches.
Fix typo in user manual
Fix bug in pg_receivexlog --verbose.

In 9.2, pg_receivexlog with verbose option has emitted the messages
at the end of each WAL file. But the commit 0b63291 suppressed such
messages by mistake. This commit fixes the bug so that pg_receivexlog
--verbose outputs such messages again.

Back-patch to 9.3 where the bug was added.
Add missing PQclear() calls into pg_receivexlog.

Back-patch to 9.3.
pg_upgrade:  remove reference to autovacuum_multixact_freeze_max_age

autovacuum_multixact_freeze_max_age was added as a pg_ctl start
parameter in 9.3.X to prevent autovacuum from running.  However, only
some 9.3.X releases have autovacuum_multixact_freeze_max_age as it was
added in a minor PG 9.3 release.  It also isn't needed because -b turns
off autovacuum in 9.1+.

Without this fix, trying to upgrade from an early 9.3 release to 9.4
would fail.

Report by EDB

Backpatch through 9.3
pg_upgrade: prevent oid conflicts with new-cluster TOAST tables

Previously, TOAST tables only required in the new cluster could cause
oid conflicts if they were auto-numbered and a later conflicting oid had
to be assigned.

Backpatch through 9.3