WIP: Transportable Optimizer Mode

I've written a contrib module that allows planning information to be
extracted from one server and transported to another server to allow SQL
analysis: Transportable Optimizer Mode (TOM).

TOM works, yet is incomplete because of the lack of a stats hook within
the server. So TOM is the application which would seek to use the recent
patch requesting stats hooks in Postgres.

I'm posting this as background to later patches that will
* re-introduce a stats hook
* complete TOM so that it works fully with the stats hook

That way we can all see where I'm going with this, and why, as well as
providing a test harness for the stats hook patches.

The main purpose of all of this is to literally "get data for Tom" -
enhance the ability of experts to diagnose SQL query plans without
requiring access to the data on remote servers. I see this as an
enabling tool that will provide more information about optimizer issues
and opportunities.

Comments welcome.

--
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support