`prif_co_reduce` fails to propagate cdata argument

`prif_co_reduce` is specified to pass the caller-provided `cdata` argument through to the invocation of `operation_wrapper`.

Due to a defect this is currently not happening in Caffeine 0.7, and instead a pointer to a stack variable owned by libcaffeine is incorrectly being passed as the `cdata` argument to `operation_wrapper`.
