add SRFI 197 (pipeline operators)

[sam-d]

adapted the reference implementation of SRFI 197 from here: https://github.com/scheme-requests-for-implementation/srfi-197/ originally developed here: https://github.com/ar-nelson/srfi-197

This code is thus licensed under MIT license and copyright (c) Adam Nelson with minor edits by myself to make it work with chez-scheme