(1) Changes to read output in visc runtime API. Assuming a pointer, size,

pointer, size ... format for PTX nodes
(2) refactoring DFG2LLVM passes. Moving all the ptx code to ptx pass.
M    llvm/projects/visc-rt/visc-rt.cpp
M    llvm/lib/Transforms/DFG2LLVM_X86/DFG2LLVM_X86.cpp
M    llvm/lib/Transforms/DFG2LLVM_NVPTX/DFG2LLVM_NVPTX.cpp