Blender Git Loki

Fix issues with node deduplication in Cycles shader graph.

It is not possible to use a set split by name as valid input to
check_node_input_traversed - it needs a complete set of all nodes visited so
far. On the other hand, the merge comparison loop should only check nodes that
were not just visited, but found unique. This means that there should really be
two separate data structures.

Without the fix, check_node_input_traversed actually never returns true, so
only nodes without any inputs are processed.