Allow queries that use "GROUP BY e1 ORDER BY e2" where e1 and e2 are identical aprt...

Allow queries that use "GROUP BY e1 ORDER BY e2" where e1 and e2 are identical aprt from ASC/DESC sort-orders to be optimized using a single index. Also allow virtual tables to optimize DISTINCT in cases where the result-set of a query does not exactly match the ORDER BY clause.

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