9435af7d1268747fb573de61f0dfc8e32508601b Fix compatibility issue with Bison 3.

================================ DYNARE MAKE CHECK MATLAB RESULTS ================================ | TOTAL: 413 | PASS: 411 | FAIL: 0 | XFAIL: 2 | XPASS: 0

================================ DYNARE MAKE CHECK OCTAVE RESULTS ================================ | TOTAL: 411 | PASS: 409 | FAIL: 0 | XFAIL: 2 | XPASS: 0

A full log can be found on karaba in '/tmp/dynare-4.4-check-e3lGpO14Wv.log'.