pgsql: Update pg_upgrade docs to show options in alphabetical order, and

Log Message:
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Update pg_upgrade docs to show options in alphabetical order, and
improve 8.3 doc limitations paragraph.

Modified Files:
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pgsql/doc/src/sgml:
pgupgrade.sgml (r1.9 -> r1.10)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pgupgrade.sgml?r1=1.9&r2=1.10)