Freeze an outer projected row in pipelined case like 54a406f891d3de31504baff74d5cd8147905d0b8 did in non-pipelined case.
merge MMcM: Freeze an outer projected row in pipelined case

Merge pull request #1249 from MMcM/sql-layer/map-nested-pipelined-freeze
https://github.com/FoundationDB/sql-layer/pull/1249