When the estimated cost to do a sort overwhelms the estimated cost to do
individual table lookups, make sure that the table lookup costs are still
taken into consideration when selecting the lookup algorithm.
Remove the extraneous debugging printf() from the previous check-in.
Clarify the computation of compatible isOrdered by in the plan solver of
the query planner.
When the estimated sorting cost overwhelms the estimated lookup cost, ensure
that lookup costs are still taken into account when selecting a lookup
algorithm.