pgsql: Fix contrib/pgstattuple and contrib/pageinspect to prevent

[tgl(at)postgresql(dot)org (Tom Lane)]

Log Message:
-----------
Fix contrib/pgstattuple and contrib/pageinspect to prevent attempts to read
temporary tables of other sessions; that is unsafe because of the way our
buffer management works.  Per report from Stuart Bishop.
This is redundant with the bufmgr.c checks in HEAD, but not at all redundant
in the back branches.

Tags:
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REL8_3_STABLE

Modified Files:
--------------
    pgsql/contrib/pageinspect:
        btreefuncs.c (r1.6 -> r1.6.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/pageinspect/btreefuncs.c?r1=1.6&r2=1.6.2.1)
        rawpage.c (r1.4 -> r1.4.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/pageinspect/rawpage.c?r1=1.4&r2=1.4.2.1)
    pgsql/contrib/pgstattuple:
        pgstatindex.c (r1.8 -> r1.8.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/pgstattuple/pgstatindex.c?r1=1.8&r2=1.8.2.1)
        pgstattuple.c (r1.32 -> r1.32.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/pgstattuple/pgstattuple.c?r1=1.32&r2=1.32.2.1)