Add `comint-environment' and `comint-pager'
- `comint-environment' is a general way to set envars for the child process.
- `comint-pager' is synched from FSF to handle just PAGER
This instance will be upgraded to Heptapod 1.5.0rc (GitLab 16.11.1) on 2024-05-02 at 15:00 UTC+2