pgsql: Fix the mechanism for reporting the original table OID and column

Log Message:
-----------
Fix the mechanism for reporting the original table OID and column number
of columns of a query result so that it can "see through" cursors and
prepared statements. Per gripe a couple months back from John DeSoi.

Modified Files:
--------------
pgsql/src/backend/access/common:
printtup.c (r1.90 -> r1.91)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/common/printtup.c.diff?r1=1.90&r2=1.91)
pgsql/src/backend/commands:
prepare.c (r1.39 -> r1.40)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/prepare.c.diff?r1=1.39&r2=1.40)
pgsql/src/backend/tcop:
postgres.c (r1.449 -> r1.450)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c.diff?r1=1.449&r2=1.450)
pquery.c (r1.93 -> r1.94)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/pquery.c.diff?r1=1.93&r2=1.94)
pgsql/src/include/commands:
prepare.h (r1.13 -> r1.14)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/commands/prepare.h.diff?r1=1.13&r2=1.14)
pgsql/src/include/tcop:
pquery.h (r1.34 -> r1.35)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/tcop/pquery.h.diff?r1=1.34&r2=1.35)