cmake: ignore unreferenced formal paramter warnings in common/vec

And remove all the hacks that were in place to avoid those warnings
vec: remove pixel-ssse3.cpp, its last function has asm coverage
cmake: ignore gcc warnings in vector intrinsic files
cmake: nits
slicetype: CuTree Implementation for AQ RateControl

Added Following methods into slicetype for CuTree Implementation
1.cuTree - Entry Point for CuTree
2.estimateCUPropagate and estimateCUPropagateCost - Calculate the CU Propagate cost for CU's
3.cuTreeFinish - update the qpOffset using Precomputed PropagateCost, weightedCostDelta and lookahead costs

Added cuTree option into param->rc and make it as a Disable, still the cuTree is an Under Construction
pixel: fix 16bpp warnings that were previously hidden by cmake rules