Fix a bug in the way that fusion determines whether a fused parfor does any work. The new code takes the union of the def of each statement that is part of a fused parfor and then subtracts out those symbols that are dead at the end of the fused parfor. This is now an accurate description of the symbols that are modified by the fused parfor. We then use this unioned with the next parfor's def set intersected with the next parfor's live out set to determine if there is any work done by the parfor. This solves issue54.
Fix a bug in the way that fusion determines whether a fused parfor does any work.
The new code takes the union of the def of each statement that is part of a fused parfor and then subtracts out those symbols that are dead at the end of the fused parfor.
This is now an accurate description of the symbols that are modified by the fused parfor.
We then use this unioned with the next parfor's def set intersected with the next parfor's live out set to determine if there is any work done by the parfor.
This solves issue54.

JuliaPackageMirrors/ParallelAccelerator.jl,malekbr/julia-to-tiramisu,IntelLabs/ParallelAccelerator.jl