Improve compatibility with old Makefile
* targets.mk: change the "local.mk" template so that "oldorg" will be
the default target for maximum compatibility. Admonish info message
with a reminder to use "make help" for more information on targets
and that "oldorg" is the default target for now. Add new
convenience target "uncompiled" that will keep the lisp directory
free from *.elc files and the autoload files up-to-date.
* Makefile: make "targets" and "helpall" depend on "help" so that only
"help::" or "helpall::" needs to be written for adding more help
messages. Useful when users want to add their own messages to "make
help" et al.