BUG #7549: max_connections check should query master when starting standby

The following bug has been logged on the website:

Bug reference: 7549
Logged by: Petteri Räty
Email address: petsku(at)petteriraty(dot)eu
PostgreSQL version: 9.2.0
Operating system: Linux or OS X
Description:

On a streaming hot standby slave starting postgres:

LOG: database system was interrupted while in recovery at log time
2012-09-17 21:29:31 EEST
HINT: If this has occurred more than once some data might be corrupted and
you might need to choose an earlier recovery target.
LOG: entering standby mode
FATAL: hot standby is not possible because max_connections = 20 is a lower
setting than on the master server (its value was 100)
LOG: startup process (PID 51494) exited with exit code 1
LOG: aborting startup due to startup process failure

It was indeed the case that the limit was lower on the slave but to resolve
it I lowered the setting on the master:

postgres=# SHOW max_connections;
max_connections
-----------------
20
(1 row)

The slave should allow resolving the issue by not only changes on the slave
side but by checking if the master has been updated as well.

Regards,
Petteri