Fixes: debbugs:20202
* lisp/net/tramp-sh.el (tramp-remote-process-environment):
* lisp/comint.el (comint-exec-1):
* lisp/term.el (term-exec-1): Don't set EMACS envvar.
* lisp/progmodes/compile.el (compilation-start): Same and bring
INSIDE_EMACS's format in line with other users.