As we merge with upstream and by that keep refining the Postgres
planner, legacy planner is no longer a suitable name. This changes
all variations of the spelling (legacy planner, legacy optimizer,
legacy query optimizer etc) to say "Postgres" rather than "legacy".
Reviewed-by: NVenkatesh Raghavan <vraghavan@pivotal.io>
Reviewed-by: NDavid Yozie <dyozie@pivotal.io>
Reviewed-by: NGeorgios Kokolatos <gkokolatos@pivotal.io>

* removing incorrect warnings stating that GPORCA is not compatible with gpperfmon db

* doc changes to support GPORCA on by default

* updating adminguide source with most recent 4.3.x work

* updating reference manual with most recent 4.3.x work

* updating utility guide with most recent 4.3.x changes

* updating client tools guide with most recent 4.3.x changes

* adding new file for client tools

* updating map files with most recent 4.3.x changes

* updating map files with most recent 4.3.x changes

* Revert "updating map files with most recent 4.3.x changes"

This reverts commit d7570343c17a126b4d11eaee3870ad6daa36966f.

* Revert "updating map files with most recent 4.3.x changes"

This reverts commit d7570343c17a126b4d11eaee3870ad6daa36966f.

* updating ditamaps with latest 4.3.x changes

* updating ditamaps with latest 4.3.x changes