Merge in "What's cooking" history

The one-file-per-issue format is not an optimal way to maintain these
documents in a self-respecting version control system.  Granted, they do
not "diff" very well, but that is something we can improve by defining a
custom diff driver for them.

"What's in" are just a glorified "git shortlog --no-merged" without any
additional comments, and I am very tempted to drop them.  I haven't
issued them for quite some time, and nobody seems to have noticed.