pgsql: Guard against duplicate IDs in input file in SortTocFromFile().

Log Message:
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Guard against duplicate IDs in input file in SortTocFromFile().
Per report from Brian Hackett.

Modified Files:
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pgsql/src/bin/pg_dump:
pg_backup_archiver.c (r1.108 -> r1.109)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_archiver.c.diff?r1=1.108&r2=1.109)