* Docs: fixing several broken links

* Docs: fixing several broken links

* Adding info about GPORCA support notice

* add missing comma

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>

* DOCS: clarify GPORCA index support
-only B-tree and bitmap indexes are supported. GPORCA ignores indexes created with unsupported indexing methods.

* docs: GPORCA index support review update - move notes to index type parameter.

-Add  GUC optimizer_enable_associativity
-Add limitation for ONLY table name qualifier  (fallback to planner)

* docs: update to GPORCA limitations
-removed window function limitation
-added aggregate functions with set operators as input

PR for 5X_STABLE
Will be ported to MAIN

* re-added PERCENTILE window function - support is for 6.0 only.

* docs: GPORCA removed limitation - multiple DISTINCT qualified aggregate functions

* docs: updates to create function attribute execute on

* docs: review comment updates for CREATE FUNCTION

* Relocates gpperfmon reference from GPCC

* Remove emcconnect history and itorators from PDF ditamap

* Remove iterator metrics subtopic from PDF ditamap

* Additional edits to acknowledge gpperfmon without GPCC

* Incorporate gpperfmon.conf reference into gpperfmon_install reference

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

* doc changes to support GPORCA on by default

* moving linux kerberos client instructions to dedicated topic, and placing it parallel with existing windows topic

* removing map and dita files for connectivity package, which is no longer provided

* removing more references to connectivity packages; conditionalizing postgres odbc/jdbc vs datadirect drivers for oss/pivotal audiences

* adding .ditaval for handling pivotal conditions; [ci skip]

* relocating pivotal ditaval

* adding .ditaval for handling pivotal conditions; [ci skip]

* relocating pivotal ditaval

* removing/fixing old references to 4.3 version

* removing pgcrypto.fips mentions

* small fix to version format

* removing 'orca' from package version strings

* changing rhel5 to rhel6 in example version strings

* 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