First step of a BIG refactor.  Replace Fold/Scan with GenReduce in CLike and GPUIR
Merge branch 'GenReduce'

Conflicts:
	Data/Array/Accelerate/BackendKit/Phase3/ToGPUIR.hs
Extract the fold strides and push them all the way through to ToCLike.hs where they can be used, but they're not used yet