Rename ++append to ++concat

[sigilante]

(which may also be occupied?)

In the userspace library, I've ruminated on alternative names. I think that we should make (both here and there) ++snoc into ++append and ++weld into ++concat.

[sigilante]

strcat? Perhaps too much of a yield to the C names.

[jackfoxy]

There is already +concat.
+snoc is kind of a special case of the append concept.

[sigilante]

Your feedback solicited on https://github.com/tamlut-modnys/userspace-util/tree/main, section /lib/list.