Hot Standby status

Attached is the latest and greatest patch against CVS head, taken from
the hs-riggs branch in my git repository.

These two TODO items I listed earlier have now been fixed:

> <done> allow connections after a shutdown checkpoint
>
> <done> don't clear locks belonging to prepared transactions at startup

And these still remain:

> - clarify default_transaction_read_only and transaction_read_only
>
http://archives.postgresql.org/message-id/4AB75A61.6040505@enterprisedb.com
>
> - rename references to "loggable locks" to "AccessExclusiveLocks in
> master" or similar
>
> - race condition in xact_redo_commit/abort
>
(http://archives.postgresql.org/message-id/4ABF539F.8050305@enterprisedb.com)
>
> - connection goes out of sync when an idle-in-transaction transaction is
> killed
>
(http://archives.postgresql.org/message-id/4ACF77A5.1070706@enterprisedb.com)

Those are pretty small things, shouldn't take long to fix. After all of
those TODO items have been addressed, the patch needs a round or two of
cleanup. Things have been moved around and changed so much that many of
the functions are probably not in a good place in code anymore.

As I said before:

> Let me know if I'm missing something. And please feel free to help, by
> testing, by reviewing and commenting on the patch, or by addressing any
> of the above issues. I will continue working on this, but this is a big
> patch so any help is much appreciated.

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com