fix bug when defining variable with value on the command line with -D option (problem introduced in ee5fc6b1)

substitute leads/lags appropriately when identification or sensitivity statements are present. Issue: dynare#1631

Problem introduced in a69c6536.

Simply redirect cout to /dev/null, instead of propagating a boolean
everywhere.

This feature is ill-designed and no longer needed by the GUI. And is not very
useful: it is not possible to interact with the preprocessor without using the
filesystem, since the preprocessor creates many files anyways.

If we really need to reimplement such a feature, it should rather be redesigned
by reading the modfile from standard input (cin). That could be triggered by
using "-" as the filename argument (as is already done by several standard Unix
utilities).

The M_.params structure was not correctly passed to
dynamic_set_auxiliary_series.m, leading to crashes if a parameter was needed to
compute an auxiliary variable (typically an auxiliayr lead variable
corresponding to a non-linear term in stochastic setup).

Since 38152c34, the M_.endo_histval variable is
generated via dynamic_set_auxiliary_dseries.m. But the latter file does not
handle auxiliary variables for Lagrange multiplier. We therefore now set them
by hand (at an initial value of zero).

Since 38152c34, the M_.endo_histval variable is
generated via dynamic_set_auxiliary_dseries.m. The problem is that, for
auxiliary variables corresponding to a lead, this will generate a NaN in
M_.endo_histval. This is conceptually correct, since such variables are never
used as initial conditions, but this is inconsistent with what we do with the
"initval" block, and leads to crashes in some routines where we fail when there
is a NaN. Therefore, replace these with a zero, as it used to be.

To install this version of gcc:

~$ brew install gcc@7

Does not seem to work with gcc-8 (missing headers…).

Ref dynare#1630

The idea is to make use of the dynamic_set_auxiliary_dseries.m file to generate
the initial conditions for all auxiliary variables, including the diffs.

Also remove the check done by the preprocessor for the lags in histval, since
it does not work correctly with the diff operator.

allow the use of previously assigned variables in epilogue block in later equations in epilogue block

- ExprNode::maxLag() and ExprNode::maxLead() now take into account exogenous
  deterministic variables, for consistency with M_.maximum_{lead,lag}

- ExprNode::maxLag() no longer behaves as if diff() operators were
  expanded (i.e. it now returns 1 on diff(x(-1))), for consistency with
  maxEndoLag() and maxExoLag()

- New ExprNode::maxLagWithDiffsExpanded() method, that behaves as maxLag() used
  to behave (except that it also takes exogenous deterministic into account)

Previously, this function was counting the total number of diff() operators in
an expression. But this is not very useful, and is potentially misleading,
because in practice we use this function to compute the maximum lag on
variables in levels.

This function now returns the maximum number of nested diffs.

For example, on diff(x)+diff(diff(y)), this function was returning 3, and it
now returns 2.

This was a bug, now fixed in Bison 3.2.2. The latter version is now available
on most platforms (Debian unstable/testing, Homebrew, MSYS2).

The data structure written in the driver file is changed also in the case of
the "variable" option.

Those const data members are simply made public.

The engine is now more robust and should reject any expression that does not
conform to the expected form. It is also able to deal with more cases, such as
terms appearing with a minus sign, or variables in the middle of a
three-factors product.

BTW, use a std::tuple for storing the result of the matching inside
PacExpectationNode, and change the order of components within the
structure (variable first, scalar last).

The preprocessor now writes all the symmetric elements in the "hp"
matrix (derivatives of the hessian w.r.t. parameters), for consistency with all
other derivatives output.

Previously it was only writing one of the two symmetric elements, when indices
of endogenous were different.

Also, no longer compute two times symmetric elements in derivation w.r.t.
parameters at order 2, for consistency with derivation w.r.t. endogenous.
It is therefore now necessary to duplicate them in the output to keep behavior
unchanged.