pgsql: Teach autovacuum how to determine whether a temp table belongs to

Log Message:
-----------
Teach autovacuum how to determine whether a temp table belongs to a crashed
backend.  If so, send a LOG message to the postmaster log, and if the table
is beyond the vacuum-for-wraparound horizon, forcibly drop it.  Per recent
discussions.  Perhaps we ought to back-patch this, but it probably needs
to age a bit in HEAD first.

Modified Files:
--------------
    pgsql/src/backend/catalog:
        namespace.c (r1.106 -> r1.107)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/namespace.c?r1=1.106&r2=1.107)
    pgsql/src/backend/postmaster:
        autovacuum.c (r1.79 -> r1.80)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/autovacuum.c?r1=1.79&r2=1.80)
    pgsql/src/backend/storage/ipc:
        sinvaladt.c (r1.72 -> r1.73)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/sinvaladt.c?r1=1.72&r2=1.73)
    pgsql/src/include/catalog:
        namespace.h (r1.53 -> r1.54)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/namespace.h?r1=1.53&r2=1.54)
    pgsql/src/include/storage:
        sinvaladt.h (r1.48 -> r1.49)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/sinvaladt.h?r1=1.48&r2=1.49)