pgsql: pg_upgrade: document possible pg_hba.conf options

pg_upgrade: document possible pg_hba.conf options
Previously, pg_upgrade docs recommended using .pgpass if using MD5
authentication to avoid being prompted for a password.  Turns out pg_ctl
never prompts for a password, so MD5 requires .pgpass --- document that.
Also recommend 'peer' for authentication too.
Backpatch back to 9.1.

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/ad4c625ee464b409f341d4680127e816391fe94f

Modified Files
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doc/src/sgml/pgupgrade.sgml |    8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)