man: document some more bus functions
swap: remove if/else with the same data path

This was introduced in e1770af812 (2012-02-03, swap: replace failure
boolean by result enum).

This just removes unneeded lines of code, no functional change.
Update .mailmap file

This commit updates email addresses of people, who are already in the
.mailmap file, so I'd assume they have sorted out their viewpoint on
privacy within the .mailmap file.

The entries for this commit have been produced using:
        # Finding out duplicates by comparing email addresses:
        git shortlog -sne |awk '{ print $NF }' |sort |uniq -d

        # Finding out duplicates by comparing names:
        git shortlog -sne |awk '{ NF--; $1=""; print }' |sort |uniq -d