dfb8f786158cbb8c4e818357f2222924dd44e7b7 doc: sbvar_identification stub, #237 (cherry picked from commit 37d18f6b690640f38c39936e146420e33c703d8b)

================================ 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-8PjkRtQazV.log'.