Add TODO items we don't want (Idea from Josh Berkus)

Add TODO items we don't want (Idea from Josh Berkus)

>
>
> Features We Do _Not_ Want
> =========================
>
> * All backends running as threads in a single process (not want)
>
>   This eliminates the process protection we get from the current setup.
>   Thread creation is usually the same overhead as process creation on
>   modern systems, so it seems unwise to use a pure threaded model.
>
> * Optimizer hints (not want)
>
>   Optimizer hints are used to work around problems in the optimizer.  We
>   would rather have the problems reported and fixed.
>   http://archives.postgresql.org/pgsql-hackers/2006-08/msg00506.php