Merge remote-tracking branch 'Dynare/master' into enterprise

Fixed conflicts in:

 - .gitlab-ci.yml
 - matlab/dynare_config.m
 - matlab/dynare_solve.m
 - matlab/initvalf.m
 - matlab/perfect-foresight-models/make_ex_.m
 - matlab/perfect-foresight-models/perfect_foresight_setup.m
 - mex/build/matlab/Makefile.am
 - mex/build/matlab/configure.ac
 - mex/build/octave/Makefile.am
 - mex/build/octave/configure.ac
 - mex/sources/Makefile.am
 - preprocessor
 - tests/Makefile.am