9d80531a51e9e8a5263fa0511e1aa97f6ba1df92 Better error message when block option when a variable does not appear at current period.

================================ DYNARE MAKE CHECK MATLAB RESULTS ================================ | TOTAL: 423 | PASS: 421 | FAIL: 0 | XFAIL: 2 | XPASS: 0

================================ DYNARE MAKE CHECK OCTAVE RESULTS ================================ | TOTAL: 421 | PASS: 419 | FAIL: 0 | XFAIL: 2 | XPASS: 0

A full log can be found on karaba in '/tmp/dynare-4.4-check-jeKvYU4Hpl.log'.