Re: a misbehavior of partition row movement (?)

I rebased this patch; v15 attached.  Other than fixing the (very large)
conflicts due to nodeModifyTable.c rework, the most important change is
moving GetAncestorResultRels into execMain.c and renaming it to have the
"Exec-" prefix.  The reason is that what this code is doing is affect
struct ResultRelInfo, which is owned by execMain.c, so it seemed bogus
to do that in nodeModifyTable.c and then let execMain.c's
ExecCloseResultRelations() do the cleanup.  I added a little commentary
in the latter routine too.

-- 
Álvaro Herrera              Valdivia, Chile  —  https://www.EnterpriseDB.com/
"World domination is proceeding according to plan"        (Andrew Morton)