pgsql: Recommend include_realm=1 in docs

Recommend include_realm=1 in docs

As discussed, the default setting of include_realm=0 can be dangerous in
multi-realm environments because it is then impossible to differentiate
users with the same username but who are from two different realms.

Recommend include_realm=1 and note that the default setting may change
in a future version of PostgreSQL and therefore users may wish to
explicitly set include_realm to avoid issues while upgrading.

Branch
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REL9_3_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/3de791ee766779f89e399da6316e0d280de6ecaa

Modified Files
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doc/src/sgml/client-auth.sgml | 41 ++++++++++++++++++++++++++++++++---------
1 file changed, 32 insertions(+), 9 deletions(-)