This isn't working, with make-base-operation changing from part of a
macro to a procedure, I'm not sure how to maintain compatability. I
think just switching to guile-fibers-next everywhere is the approach
to take.
This reverts commit f41d1853ce.
As the implementation of this changed in fibers, and that's causing
issues here when mixing the version of fibers used for knots and
different versions of fibers.
