pgsql: Limit pg_upgrade authentication advice to always-secure techniqu

Limit pg_upgrade authentication advice to always-secure techniques.

~/.pgpass is a sound choice everywhere, and "peer" authentication is
safe on every platform it supports.  Cease to recommend "trust"
authentication, the safety of which is deeply configuration-specific.
Back-patch to 9.0, where pg_upgrade was introduced.

Branch
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REL9_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/f0af51d077b392cac4ce25e1347a4fc3b050d832

Modified Files
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doc/src/sgml/pgupgrade.sgml |   14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)