pgsql: Make pg_dump/pg_restore --clean options drop large objects too.

Log Message:
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Make pg_dump/pg_restore --clean options drop large objects too.
In passing, make invocations of lo_xxx functions a bit more schema-safe.

Itagaki Takahiro

Modified Files:
--------------
pgsql/src/bin/pg_dump:
pg_backup_archiver.c (r1.172 -> r1.173)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_archiver.c?r1=1.172&r2=1.173)
pg_backup_archiver.h (r1.79 -> r1.80)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_archiver.h?r1=1.79&r2=1.80)
pg_backup_custom.c (r1.42 -> r1.43)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_custom.c?r1=1.42&r2=1.43)
pg_backup_files.c (r1.35 -> r1.36)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_files.c?r1=1.35&r2=1.36)
pg_backup_null.c (r1.20 -> r1.21)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_null.c?r1=1.20&r2=1.21)
pg_backup_tar.c (r1.65 -> r1.66)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_tar.c?r1=1.65&r2=1.66)