pgsql: Modify the relcache to record the temp status of both local and

Log Message:
-----------
Modify the relcache to record the temp status of both local and nonlocal
temp relations; this is no more expensive than before, now that we have
pg_class.relistemp.  Insert tests into bufmgr.c to prevent attempting
to fetch pages from nonlocal temp relations.  This provides a low-level
defense against bugs-of-omission allowing temp pages to be loaded into shared
buffers, as in the contrib/pgstattuple problem reported by Stuart Bishop.
While at it, tweak a bunch of places to use new relcache tests (instead of
expensive probes into pg_namespace) to detect local or nonlocal temp tables.

Modified Files:
--------------
    pgsql/src/backend/catalog:
        index.c (r1.314 -> r1.315)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/index.c?r1=1.314&r2=1.315)
        namespace.c (r1.116 -> r1.117)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/namespace.c?r1=1.116&r2=1.117)
        toasting.c (r1.13 -> r1.14)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/toasting.c?r1=1.13&r2=1.14)
    pgsql/src/backend/commands:
        analyze.c (r1.134 -> r1.135)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/analyze.c?r1=1.134&r2=1.135)
        cluster.c (r1.182 -> r1.183)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/cluster.c?r1=1.182&r2=1.183)
        copy.c (r1.306 -> r1.307)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/copy.c?r1=1.306&r2=1.307)
        indexcmds.c (r1.182 -> r1.183)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/indexcmds.c?r1=1.182&r2=1.183)
        tablecmds.c (r1.280 -> r1.281)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c?r1=1.280&r2=1.281)
        vacuum.c (r1.386 -> r1.387)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuum.c?r1=1.386&r2=1.387)
    pgsql/src/backend/optimizer/prep:
        prepunion.c (r1.167 -> r1.168)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/prep/prepunion.c?r1=1.167&r2=1.168)
    pgsql/src/backend/postmaster:
        autovacuum.c (r1.93 -> r1.94)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/autovacuum.c?r1=1.93&r2=1.94)
    pgsql/src/backend/storage/buffer:
        bufmgr.c (r1.249 -> r1.250)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/buffer/bufmgr.c?r1=1.249&r2=1.250)
    pgsql/src/backend/utils/cache:
        relcache.c (r1.285 -> r1.286)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/cache/relcache.c?r1=1.285&r2=1.286)
    pgsql/src/include/utils:
        rel.h (r1.112 -> r1.113)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/rel.h?r1=1.112&r2=1.113)