Make install target functional for new eln-cache directory arrangement

Make install target functional for new eln-cache directory arrangement

	* src/comp.h (fixup_eln_load_path): New extern.

	* src/comp.c (fixup_eln_load_path): New function.

	* src/pdumper.c (dump_do_dump_relocation): Update to make use of
	'fixup_eln_load_path'.

	* lisp/loadup.el: Update to store in the compilation unit the
	correct eln-cache installed path. Rename --lisp-dest -> --eln-dest
	and.

	* Makefile.in: Pass the eln destination directory to
	src/Makefile. Rename LISP_DESTDIR -> ELN_DESTDIR.
	(ELN_DESTDIR): Define.
	(install-eln): New target.
	(install): Add install-eln as prerequisite.

	* src/Makefile.in: Rename --lisp-dest -> --eln-dest and
	LISP_DESTDIR -> ELN_DESTDIR.