b5ca118bfb3a062daf0fdbd086e57c020e4e011a trust_region: replace a loop with a matrix expression

================================ DYNARE MAKE CHECK MATLAB RESULTS ================================ | TOTAL: 444 | PASS: 442 | FAIL: 0 | XFAIL: 2 | XPASS: 0

================================ DYNARE MAKE CHECK OCTAVE RESULTS ================================ | TOTAL: 442 | PASS: 440 | FAIL: 0 | XFAIL: 2 | XPASS: 0

A full log can be found on karaba in '/tmp/dynare-master-check-zL7ZoUq9hc.log'.