Dropped usage of VectorClass
Goes together with LHCb!2645 (merged)
Note that some piece of code in the QuarticSolverNewton goes back to scalar and thus potentially becomes slower with this change. I could not manage to apply the modifications applied on master as nothing has been backported there in the last 3 years and the code has diverged too much. @jonrob for info.
Edited by Marco Cattaneo