Separate cleanup from ctype review, namely:
- Simplify the source dir specification, and update README appropriately
- Drop the LC (doonly) processing, it's broken, and even if fixed, not really useful
- Don't remove the target directories while installing new data as it removes Makefile.depend which we don't manage; only rm the files we are going to add/replace/delete instead
- Restrict adding bsd.endian.mk to colldef and ctypedef Makefiles, it's not needed in other (text-only) categories
- GC unused scripts; they don't seem to be particularly helpful standalone as well