In particular, in the case of an 'mcp' tag, this could lead to a convergence
failure.

Also modify the lmmpc/rbcii.mod test so that it fails if convergence is not
obtained, in order to detect such regressions earlier.

Closes: #1697

This preprocessor update also includes the following changes:
— removal of license.txt, now merged in back in the main Dynare one
– various code simplifications and modernizations in the macro processor
— minor code simplification in parsing of the --+ options: … +-- line