mkstr and xstr should be ejected

These utilities are really, really ancient programs designed to facilitate building programs to share command messages and strings. The intention being to minimize memory impact on systems like the PDP-11. We're long past that time, and I've never ever seen a case of either of these programs being used in the wild.

Furthermore, modern optimizers can replace constant strings (-xstrconst) to single references.

Its time to throw this baggage away.