pgsql: Stress that backup_label file is critical in the docs.

Stress that backup_label file is critical in the docs.

It is surprisingly common mistake to leave out backup_label file from a base
backup. Say more explicitly that it must be included.

Jeff Janes, with minor rewording by me.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/7f03a791fa131eb20c6df07740522163d8b3c94e

Modified Files
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doc/src/sgml/backup.sgml |   11 +++++++----
1 files changed, 7 insertions(+), 4 deletions(-)