use leads and lags in #declarations, as allowed by  4f6344e6 (see also #1929).

See merge request Dynare/dynare!2305

 selec_posterior_draws.m: correct index (bug introduced in dc9560e6)

See merge request Dynare/dynare!2307

added Irreversible_investment_leadlag.mod to testsuite and make comparison with Irreversible_investment.mod

provide alternative irreversible investment model that uses leads and lags in #declarations, as allowed by 4f6344e6 (see also #1929).
check consistency with results of the original model

Add DIME MCMC

See merge request Dynare/dynare!2301

smc_samplers_initialization.m: clean up header

See merge request Dynare/dynare!2302

 - Fix range with --print-table option.
 - Add interpolation for flow variables (annual to quaterly)

Fix implementations of multivariate Student distribution

See merge request Dynare/dynare!2303

[skip ci]

Use empty() method instead of size() to test for non-emptyness of a container.

Workaround for preprocessor#130.

– Macroprocessor: print line numbers in the output of @#echomacrovars (without “save” option)
– Correctly handle whitespaces when parsing contents of legacy “mcp” tags
– Misc simplifications and C++20 modernizations

Ref. #1859