It is therefore now possible to write:

  static_model = static_cast<StaticModel>(dynamic_model);

In particular, it is necessary to turn back DataTree::AddVariable() into a
non-virtual method, because it is called from DataTree's constructor. Enforcing
the absence of leads/lags is now done using a new boolean DataTree::is_static.

Take advantage of the new copy constructor for handling
PlannerObjectiveStatement more elegantly.

Unfortunately it is not possible to implement *move* constructor / assigment
operators, because the reference ExprNode::datatree is not mutable.

This facilitates switching variable types on the fly. In particular, this
allows removing the hack in DynamicModel::updateAfterVariableChange() that way
basically recreating all the nodes after the type change.

The syntax makes clearer the distinction between a function call and an
initialization. Also, it prevents bugs due to implicit type conversions.

Closes: dynare#1315

This mimicks the structure of M-functions (though the logic for filling the
temporary terms vector is a bit different).

This change implied a modification in the way we compute the checksum in case
of block decomposition (the temporary terms for the C output are not correctly
computed in that case).

Adds a new model option "linear_decomposition" that creates a block composed of the non-linear equations o the model

Since model local variables are now treated as temporary terms, they must be
marked as such even when option notmpterms is present.

Incidentally, replace the IS_* macros by inline functions.

ensure that trend_variable found is actually a trend variable as declared in the trend_component_model statement

Given a previously declared var_model, the var_expectation_model statement is
used to declare a way of forming expectations with this VAR (possibly using a
finite or infinite discounted sum). The var_expectation operator now takes a
single argument, the name of the var_expectation_model.

For the moment, this only works when the var_model is using equations
explicitly declared in the model block.

See McModelTeam/McModelProject/issues/97.

aux_equations only contain the definition of auxiliary variables, and
may diverge from those in the main model (equations), if other model
transformations applied subsequently. This is not a problem, since
aux_equations is only used for regenerating the values of auxiliaries
given the others.

For example, such a divergence appears when there is an expectation
operator in a ramsey model, see
tests/optimal_policy/nk_ramsey_expectation.mod */