Rework environment variable support. (Reported by Kalle Olavi Niemitalo and Noah...

Rework environment variable support.  (Reported by Kalle Olavi Niemitalo and Noah Friedman.)

* src/callproc.c (Vglobal_environment, Vlocal_environment_variables): Remove.
  (getenv_internal, child_setup): Don't look at global-environment or
  local-environment-variables.
  (Fgetenv_internal): Update docs.
  (set_initial_environment): Rename from set_global_environment.  Store
  Emacs environment in initial frame parameter.
  (syms_of_callproc): Remove obsolete defvars.  Update docs.

* lisp/env.el (read-envvar-name): Remove reference to global-environment.
  (setenv-internal): New function.
  (setenv): Use it.  Always set process-environment.  Update docs.
  (getenv): Update docs.
  (environment): Rewrite for the new environment design.  Update docs.

* lisp/frame.el (frame-initialize): Copy the environment from the initial frame.

* src/emacs.c (main): Call set_initial_environment, not set_global_environment.

git-archimport-id: lorentey@elte.hu--2004/emacs--multi-tty--0--patch-569