This reverts merge request !9

not). Code generation uses it.
- Added a policy that uses it.

Tested on pipeline benchmark.

Compiles correcctly for all targets and target combinations,
pending fix in python script for llvm 4.0 -> llvm 3.4

for allocation nodes.

(benchmark not updated)

Bug fix in nvptx and spir backends related to adding arguments to
node functions.

(CPU/GPU/SPIR) based on policy.
Support for scheduling per iteration included.
Further testing required.

The SymVT stuff has not been moved yet, I removed it for now.
The test/VISC tests also have not been moved yet, so they may not
work.

get_global_size
(2) Code gen for nvvm intrinsics in GenVISC pass
(3) Commented out code added to GenVISC and DFG2LLVM_X86 to allow wait
instruction in a different BB than launch (with phi nodes as uses of launch)