introduce .mailmap

introduce .mailmap

Some of us use(d) various names or emails interchangeable over the years/currently.
git integrated tools can help to count how many people contributed to a release,
the use of mailmap (https://www.kernel.org/pub/software/scm/git/docs/git-shortlog.html)
helps to map authors+email.

If I used the wrong prefered primary name+email, change it yourself.
Only it yourself in this file if you used more than one name/email.