COPYable logs status

[summarising discussion on -patches]

The situation with this patch is that I now have it in a state where I 
think it could be applied, but there is one blocker, namely that we do 
not have a way of preventing the interleaving of log messages from 
different backends, which leads to garbled logs. This is an existing 
issue about which we have had complaints, but it becomes critical for a 
facility the whole purpose of which is to provide logs in a format 
guaranteed to work with our COPY command.

Unfortunately, there is no solution in sight for this problem, certainly 
not one which I think can be devised and implemented simply at this 
stage of the cycle. The solution we'd like to use, LWLocks, is not 
workable in his context. In consequence, I don't think we have any 
option but to shelve this item for the time being.

A couple of bugs have been found and fixes identified, during the review 
process, so it's not a total loss, but it is nevertheless a pity that we 
can't deliver this feature in 8.3.

cheers

andrew