steady_state operator + oo_.steady_state versus dr.ys
The steady_state operator is currently implemented via the global variable oo_.steady_state in *_dynamic.m
It would be preferable to pass it as argument
It is also necessary to clarify the respective role of oo_.steady_state and dr.ys
In perfect foresight models where the terminal steady state is different from the initial one, we need to clarify which steady state the steady_state operator refers to.
Whatever change is made, must be done for __dynamic.m *dynamic.mex and in bytecode