Adding README files to source

As people start understanding certain areas of the code, would you
please send in a README file for that directory, so future developers
can be aided by your knowledge of how things work?

I have done README files for the parser and optimizer, but many more
need to be done or added to.

Vadim is adding one to the optimizer/planner about subselects, and
perhaps Massimo can add to the lock README file.  A good README would
have helped me a lot in adding the deadlock detection code.  I had to
figure it out myself instead.

These README's can be added up to the last day of release because they
don't affect the code.

-- 
Bruce Momjian
maillist@candle.pha.pa.us