pgsql: Repair oversight in 8.2 change that improved the handling of

Log Message:
-----------
Repair oversight in 8.2 change that improved the handling of "pseudoconstant"
WHERE clauses.  createplan.c is now willing to stick a gating Result node
almost anywhere in the plan tree, and in particular one can wind up directly
underneath a MergeJoin node.  This means it had better be willing to handle
Mark/Restore.  Fortunately, that's trivial in such cases, since we can just
pass off the call to the input node (which the planner has previously ensured
can handle Mark/Restore).  Per report from Phil Frost.

Tags:
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REL8_2_STABLE

Modified Files:
--------------
    pgsql/src/backend/executor:
        execAmi.c (r1.89 -> r1.89.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execAmi.c.diff?r1=1.89&r2=1.89.2.1)
        nodeResult.c (r1.34.2.2 -> r1.34.2.3)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeResult.c.diff?r1=1.34.2.2&r2=1.34.2.3)
    pgsql/src/include/executor:
        nodeResult.h (r1.22 -> r1.22.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/nodeResult.h.diff?r1=1.22&r2=1.22.2.1)