pgsql: Rename pg_restore -m to -j, and add documentation about what good

Log Message:
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Rename pg_restore -m to -j, and add documentation about what good numbers
are. per discussion on hackers

Modified Files:
--------------
pgsql/doc/src/sgml/ref:
pg_restore.sgml (r1.80 -> r1.81)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_restore.sgml?r1=1.80&r2=1.81)
pgsql/src/bin/pg_dump:
pg_backup.h (r1.50 -> r1.51)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup.h?r1=1.50&r2=1.51)
pg_backup_archiver.c (r1.167 -> r1.168)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_archiver.c?r1=1.167&r2=1.168)
pg_restore.c (r1.95 -> r1.96)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_restore.c?r1=1.95&r2=1.96)