* modules/putenv-gnu: Renamed from modules/putenv.
(Description): Mention the removal of environment variables.
* modules/putenv-gnu-tests: Renamed from modules/putenv-tests.
* modules/putenv: New file, an indirection to the new module.
* doc/posix-functions/putenv.texi: Mention the new module name.
* NEWS: Mention the change.
