Similarly to Vector, it now uses a std::shared_ptr for managing the underlying
data.

M_.endo_names and M_.exo_names are cell arrays, no need to use deblank to
remove trailing whitespaces.

Since the introduction of the --burn option (in Dynare++ shipped with Dynare
4.3.0), the IRFs reported by Dynare++ were wrong.

The IRFs are computed using a generalized IRF method: the result is
the (average) difference between a simulation with shock and a simulation
without shock. The problem was that the two simulations were not using the same
starting point.

Closes #1634

discretionary_policy_1.m: check for NaN before checking for non-zero derivatives

See merge request !1644

mr_hessian.m: prevent infinite loop

Closes #1636

See merge request Dynare/dynare!1645

Document treatment of several Matlab statements in one line

See merge request !1646

Related to #1637

Make sure hessian is not 0 and add counter.
Fixes #1636

Prevents false error message

[skip ci]

Fixes 4.6

See merge request Dynare/dynare!1641

 - Only works with backward models.
 - Probably doesn't work if the model includes auxiliary variables.
 - Assumes that the trends are multiplicative.

At the end of a thread, we must first notify the main thread waiting on the
condition variable, then unlock the mutex. We must do these two operations in
that order, otherwise there is a possibility of having the main process
destroying the condition variable before the thread tries to notify it (if all
other threads terminate at the same time and bring the counter down to zero).
For that reason, we cannot use std::notify_all_at_thread_exit().

Bug introduced in commit 752a02a3.

GCC 5 supports C++14, but it is still not enough because it does not implement
N4387 that was retroactively applied to the standard in 2015 (see the "Notes"
and "Defect reports" sections of
https://en.cppreference.com/w/cpp/utility/tuple/tuple).

Another version is already under tests/trend_var/ directory.

Also fix extensions of source files.