pgsql: Make the columns is_insertable_into and is_updatable behave

Log Message:
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Make the columns is_insertable_into and is_updatable behave uniformly
correctly.  They are supposed to examine which kinds of rules are present,
which they did in some of the info schema views but not in others.

Modified Files:
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    pgsql/src/backend/catalog:
        information_schema.sql (r1.48 -> r1.49)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/information_schema.sql?r1=1.48&r2=1.49)