MATLAB compatibility fix: skip mode_compute=3 test under R2009b

In this version, fminunc fails due to Inf value.

tests/optimizers/fs2000_3.mod

 @#include "fs2000.common.inc"
 
-if exist('fminunc','file')
+% Skip the test under R2009b, because fminunc fails due to Inf value.
+% It remains to be determined in which version it started to work.
+if exist('fminunc','file') && (isoctave || ~matlab_ver_less_than('7.10'))
   estimation(mode_compute=3,order=1, datafile='../fs2000/fsdat_simul', nobs=192, mh_replic=0);
 end