pgsql: Better solution to the problem of labeling whole-row Datums that

Log Message:
-----------
Better solution to the problem of labeling whole-row Datums that are
generated from subquery outputs: use the type info stored in the Var
itself.  To avoid making ExecEvalVar and slot_getattr more complex
and slower, I split out the whole-row case into a separate ExecEval routine.

Modified Files:
--------------
    pgsql/src/backend/access/common:
        heaptuple.c (r1.101 -> r1.102)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/common/heaptuple.c.diff?r1=1.101&r2=1.102)
    pgsql/src/backend/executor:
        execQual.c (r1.182 -> r1.183)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execQual.c.diff?r1=1.182&r2=1.183)