It seems there are enough people out there still on Emacs 24 to warrant undoing
some of my recent moves away from eieio to cl-generic. For the near future I
will try to keep any changes that are incompatible with Emacs 24 to a
development branch. There is still probably plenty of opportunity to make the
code more future-proof for an eventual move away from eieio (I'm looking at you
oref and sref...)