Merge tools.

[Alan Conway]

I propose we use http://www.orcaware.com/svn/wiki/Svnmerge.py to track 
merges for us. It will make merging much less error prone. I'm going to 
try it out on the 0-9 branch to backmerge and merge python and spec 
prior to merging them to trunk. Its endorsed by the svn team and 
included in the svn distribution. It can be used in conjunction with 
manual merges but life will be simpler if we always use it for all merges.

Cheers,
Alan.