Re: [PATCH] release.py: write-changelog function (POC)

After some further thought and tweaking, I committed a write-changelog
function in r1818988.

I tried to make it flexible enough so we can experiment a bit with it.

- The "changes labels" can be used as prefix or suffix.
- They can be [U:client], [D:api], ... or [U], [D], or simply []
- There's an option --include-unlabeled-summaries to include summary
lines without a label, unless [skip], [ignore], [c:skip] or [c:ignore]
is found somewhere in the commit message. Summary lines containing
'STATUS', 'CHANGES', 'Post-release housekeeping' or 'Follow-up' are
ignored.

I guess further tweaks will come up if / when we start to use this.
Also, feel free to improve the code ... I'm far from a python expert
(depending heavily on copy-paste and StackOverflow).

We might need to do something special with the words 'Revert' and
'Merge', but I'm not yet sure what.

-- 
Johan