pgsql: I have added a define, MAKE_ALL_TUPLES_VISIBLE, to help people

Log Message:
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I have added a define, MAKE_ALL_TUPLES_VISIBLE, to help people recover
deleted tuples. Of course it is only to be used for disaster recovery.

Modified Files:
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pgsql/src/backend/utils/time:
tqual.c (r1.81 -> r1.82)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/time/tqual.c.diff?r1=1.81&r2=1.82)