Full page writes improvement, code update

Hi,

Here's an update of a code to improve full page writes as proposed in

http://archives.postgresql.org/pgsql-hackers/2007-01/msg01491.php
and
http://archives.postgresql.org/pgsql-patches/2007-01/msg00607.php

Update includes some modification for error handling in archiver and
restoration command.

In the previous threads, I posted several evaluation and shown that we
can keep all the full page writes needed for full XLOG crash recovery,
while compressing archive log size considerably better than gzip, with
less CPU consumption. I've found no further objection for this proposal
but still would like to hear comments/opinions/advices.

Regards;

--
Koichi Suzuki