Epilogue variables can have leads/lags when appearing on the RHS of the
epilogue block.

The method VariableNode::maxLagWithDiffsExpanded() was already handling them,
so this commit adapts other methods for consistency.

HANK support: modifies the driver file writing process to introduce a...

See merge request Dynare/preprocessor!108

HANK support: modifies the driver file writing process to introduce a `state_var` field in the `M_.heterogeneity(i)` structure for each heterogeneity dimension `i`

This rule is obviously incorrect (and useless):
– it begins with an unescaped dollar sign, which can only match an end-of-line
  (so it makes no sense to have it at the beginning of the rule)
– it prints to standard output, which is obviously not the intended action

The driver was calling “clear” before “global”, hence clearing local and not
global variables (unless “global” had already been called at scope).

Rather use “clearvars -global”.

– New “heterogeneity_dimension” statement
– New option “heterogeneity” to “var”, “varexo”, “parameters”, “model” and
  “shocks” statements
– New “SUM()” operator in “model” block

Uses:
– structured bindings
– std::map::contains and std::map::at
– std::boolalpha and std::noboolalpha

std::fill takes a range that is open on the right bound (i.e. [first, last) and
not [first, last]).

[skip ci]

Closes: #128

It was previously in case-sensitive alphabetical order (i.e. ASCII order).

Ref. #128