Stop ns builds setting the EMACSLOADPATH environment variable
Ref bugs 4309, 6401, etc.
This is the last environment variable (ab)used by the ns port in this way.
* src/nsterm.m (ns_load_path): Rename from ns_init_paths.
Now it does not set EMACSLOADPATH, just returns the load-path string.
* src/nsterm.h: Update accordingly.
* src/lread.c [HAVE_NS]: Include nsterm.h.
(init_lread) [HAVE_NS]: Use ns_load_path.
* src/emacs.c (main) [HAVE_NS]: No longer call ns_init_paths.