Fix NS native compilation builds

Fix NS native compilation builds

* Makefile.in (ns_applibexecdir):
(ns_applibdir):
(ns_appdir): New variables.
(.PHONY): Include new rule.
(epaths-force-ns-self-contained): Remove the app bundle directory from
all paths.
* configure.ac (NS_SELF_CONTAINED): Set the default site-lisp
directory instead of hard-coding it in the ObjC code, and use the new
epaths generating make rule.
* src/callproc.c (init_callproc_1):
(init_callproc): Remove all the NS specific code as the special cases
are now handled by decode_env_path.
* src/emacs.c (load_pdump):
(decode_env_path): Use ns_relocate to find the correct directory after
relocation.
* src/lread.c (load_path_default): Remove all the NS specific code as
the special cases are now handled by decode_env_path.
* src/nsterm.h: Update function definitions.
* src/nsterm.m (ns_etc_directory):
(ns_exec_path):
(ns_load_path): Remove functions that are no longer needed.
(ns_relocate): New function to calculate paths within the NS app
bundle.
* nextstep/Makefile.in (ns_applibexecdir): New variable, and update
anything relying on the libexec location.