Hi Y'all!

I have an efficient, almost done implementation of srfi-121. I believe it lacks generator-unfold, but that is all. make-coroutine-generator is implemented using delimited continuations and runs a lot faster than the one in the reference implementation, with the caveat that it is apparently slightly incompatible: the coroutine generator usage in (srfi 146 hash) yielded the wrong result - despite my version passing all tests.