Splitting MAKEDEV.subr from MAKEDEV has caused much more trouble than I
anticipated.  I now suggest:

1. move all the function definitions back into MAKEDEV;

2. delete MAKEDEV.subr;

3. Add a way to use MAKEDEV as a function library via ". MAKEDEV".
   This can be implemented by adding a line like

      [ -n "${MAKEDEV_AS_LIBRARY}" ] && return

   after the function definitions buf before doing any real work.

4. Let MAKEDEV.local use "MAKEDEV_AS_LIBRARY=1 . MAKEDEV" to get the
   function definitions directly from MAKEDEV without MAKEDEV.subr
   existing at all.

--apb (Alan Barrett)