* plugin-runner.c (add_environment): Never insert existing environment variables. (main): Rename "--global-envs" to "--global-env" and "--envs-for" to "--env-for".
* plugin-runner.xml (SYNOPSIS): Rename "--global-envs" to "--global-env" and "--envs-for" to "--env-for". (OPTIONS): Added "--global-env" and "--env-for". (FALLBACK): Add id attribute. (EXIT STATUS): Add text. (ENVIRONMENT): New section. (FILES): Document configuration file.