[merge] doc: coding standards for repr methods

[Michael Hudson]

Martin Pool wrote:
> Patch says it all, I think.  I have been doing this in some places and
> think it is very useful.

Do you think it's worth adding something about how the strings returned 
by __repr__ shouldn't be more than a couple of hundred bytes long, if 
you agree with me that this is a good idea?  I've had some irritating 
experiences lately with repr strings that are a few kb long...

Cheers,
mwh