Closes: #124

The old name is still accepted, but will trigger a deprecation warning.

Automatically detected by clang-tidy with performance-move-const-arg check.

Do not make the modification for Tokenizer::location type, since we have no
guarantee that the type will remain trivially-copyable in the future.

Avoids an unnecessary copy.

Related to dynare#1888

The implementation no longer relies on ramsey_policy.m at the MATLAB/Octave
level.

By the way, drop ModFileStructure::ramsey_model_present, which is now
redundant.

This restriction no longer exists, and is actually not applied to stoch_simul
when following ramsey_model.

Options “order”, “partial_information” and “k_order_solver” are not accepted by
the command (this code is probably a remnant of the deprecated “ramsey_policy”
command).

And set them before any computation is done.

These fields should rather be in M_.

It was erroneously using MATLAB costs, leading to possible
inefficiencies (though those cost tables are probably not very accurate and
should be revised).

Previously, the MinGW location was appended multiple times to the PATH
variable, which in some cases would make the variable too long and thus
dysfunctional.

The variable is now initialized once when the worker threads are created.

By the way, move the macOS+Octave environment variable initializations to the
same place, for consistency.

In particular, use a std::variant to store the values of options. This ensures
that a given option name can have only one value (previously, for a given
option name, it was possible to store several values as long as they were of
different types).

The local value of option was not copied to the top-level “options_” structure,
as it is done for “nograph” and “nodisplay”.

If block decomposition fails, error out if “block” option was passed, but not
otherwise.

This commit does not modify the generated files.

This is a preliminary step for dynare#1859.

As a consequence, add many [[maybe_unused]] attributes for legitimate
cases (mainly in virtual functions).

In particular, use this feature in many loops which feature a special treatment
for the first iteration, using a boolean variable (replacing iterator
manipulation). By the way, also use std::exchange() to simultaneously test the
value of this variable and update it.