Makefile: add elint to compilation methods, ensure *.elc files exist after compilation

Makefile: add elint to compilation methods, ensure *.elc files exist after compilation

* lisp/Makefile: Add targets `slint3´ (one Emacs process for all
  sources) and `slint4´ (one Emacs instance for each source) using
  ELINTL and ELINTF to lint lisp files.  Split out compile actions
  into internal targets and implement `compile-*´ targets in terms of
  these internal targets.  Follow all targets that do not
  procude *.elc files with `dirall´ so that the *.elc files exist at
  the end of compilation.

* default.mk: Add configuration variables ELINTL and ELINTF.

* targets.mk: Add ELINTL and ELINTF to CONF_CALL.