Port to C++11 using keyword

src/ComputingTasks.hh

src/DataTree.hh

src/DynamicModel.hh

src/ExprNode.hh

src/MinimumFeedbackSet.hh

src/ModelTree.hh

src/Shocks.hh

src/SigmaeInitialization.hh

src/StaticModel.hh

src/SymbolTable.hh