Add remaining <unknown>s and comments to .mailmap

Summary:
All done, except for these 2 empty commits:

$ git log --author=unknown --use-mailmap --oneline
7e5c2b23 [project @ 2001-12-06 10:17:35 by mbs] Established under cvs.
64565981 [project @ 2000-12-01 10:33:41 by cryder] Initial revision

Reviewers: hvr, austin

Reviewed By: austin

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D477