pgsql: Phase 1 of fix for 'SMgrRelation hashtable corrupted' problem.

Log Message:
-----------
Phase 1 of fix for 'SMgrRelation hashtable corrupted' problem.  This
is the minimum required fix.  I want to look next at taking advantage of
it by simplifying the message semantics in the shared inval message queue,
but that part can be held over for 8.1 if it turns out too ugly.

Modified Files:
--------------
    pgsql/src/backend/access/transam:
        xlogutils.c (r1.35 -> r1.36)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlogutils.c.diff?r1=1.35&r2=1.36)
    pgsql/src/backend/catalog:
        heap.c (r1.278 -> r1.279)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/heap.c.diff?r1=1.278&r2=1.279)
        index.c (r1.243 -> r1.244)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/index.c.diff?r1=1.243&r2=1.244)
    pgsql/src/backend/commands:
        tablecmds.c (r1.141 -> r1.142)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.141&r2=1.142)
    pgsql/src/backend/postmaster:
        bgwriter.c (r1.12 -> r1.13)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/bgwriter.c.diff?r1=1.12&r2=1.13)
    pgsql/src/backend/rewrite:
        rewriteDefine.c (r1.99 -> r1.100)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/rewrite/rewriteDefine.c.diff?r1=1.99&r2=1.100)
    pgsql/src/backend/storage/buffer:
        bufmgr.c (r1.184 -> r1.185)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/buffer/bufmgr.c.diff?r1=1.184&r2=1.185)
        localbuf.c (r1.61 -> r1.62)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/buffer/localbuf.c.diff?r1=1.61&r2=1.62)
    pgsql/src/backend/storage/smgr:
        smgr.c (r1.84 -> r1.85)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/smgr/smgr.c.diff?r1=1.84&r2=1.85)
    pgsql/src/backend/utils/cache:
        inval.c (r1.68 -> r1.69)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/cache/inval.c.diff?r1=1.68&r2=1.69)
        relcache.c (r1.214 -> r1.215)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/cache/relcache.c.diff?r1=1.214&r2=1.215)
    pgsql/src/include/storage:
        smgr.h (r1.49 -> r1.50)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/smgr.h.diff?r1=1.49&r2=1.50)
    pgsql/src/include/utils:
        rel.h (r1.81 -> r1.82)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/rel.h.diff?r1=1.81&r2=1.82)
        relcache.h (r1.47 -> r1.48)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/relcache.h.diff?r1=1.47&r2=1.48)