pgsql: Revert "Fix bug in checking of IDENTIFY_SYSTEM result."

Revert "Fix bug in checking of IDENTIFY_SYSTEM result."

This reverts commit 083d29c65b7897f90c70e6dc0a4240a5fa75c8f2.

The commit changed the code so that it causes an errors when
IDENTIFY_SYSTEM returns three columns. But which prevents us
from using the replication-related utilities against the server
with older version. This is not what we want. For that
compatibility, we allow the utilities to receive three columns
as the result of IDENTIFY_SYSTEM eventhough it actually returns
four columns in 9.4 or later.

Pointed out by Andres Freund.

Branch
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REL9_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/e0d010f64ca2b3b7d41ca961549388cf4fbe8aed

Modified Files
--------------
src/backend/replication/libpqwalreceiver/libpqwalreceiver.c |    4 ++--
src/bin/pg_basebackup/pg_basebackup.c                       |    4 ++--
src/bin/pg_basebackup/pg_receivexlog.c                      |    4 ++--
src/bin/pg_basebackup/receivelog.c                          |    4 ++--
4 files changed, 8 insertions(+), 8 deletions(-)