PITR Archive Recovery plus WIP PITR

A number of you have pointed out that the last patch had a number of
problems, thank you all. This patchset supercedes all previous versions,
and is the only one that will work against current CVS tip.

cd pgsql/src
patch -p0 < pitr_v5_0.patch

then place

pgarch.c in src/backend/postmaster
pgarch.h in src/include

Read the README - its long and you wont have a clue without it

...remember, you HAVE TO run this on a cluster created by initdb within
the last 2-3 days...

When you perform a recovery, you can use the example recovery.conf
provided here. (Not all of the options work yet...) Just place this file
in PGDATA then crank up the postmaster any way you choose.

Known issues:
- CREATE DATABASE will not be recovered (at present)...create a new
database BEFORE you take a full physical backup
- error handling in the archiver has some issues, and requires a few
improvements...
- PITR support is partially complete in this patch - its a Work in
Progress (WIP), but doesn't interfere with other operations - I will
continue to work on this

...but this works - so please don't be put off from giving it a try - it
will take a while to get used to the concepts behind it all.

Earlier versions
- much of the code for recovery is in xlog.c - refactoring proved
difficult and a big timewaster when the main functions aren't all there
yet
- error messages streamlined
- variable naming more consistent than earlier versions

Best Regards, Simon Riggs