7438dae0d45ffd6b46c1b9c596d04da81481cf97 Speeds up the Kalman smoother (cherry picked from commit ae72105b5c0cc1cd5121e8c026d9c0bfe40dfc39)

================================ 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-Ep20HhqSyH.log'.