Improve debug mode.

tests/kalman/likelihood/test_kalman_mex.m

-debug = true;
+debug = false;
 
+if ~debug
     source_dir = getenv('source_root');
     addpath([source_dir filesep 'matlab']);
-
     dynare_config;
-
     addpath([source_dir filesep 'tests' filesep 'kalman' filesep 'likelihood']);
+end
 
 testFailed = 0;
 
@@ -79,8 +79,9 @@ catch
     end
 end
 
-t1 = clock;
 
+if ~debug
+    t1 = clock;
     fprintf('\n*** Elapsed time (in seconds): %.1f\n\n', etime(t1, t0));
-
     quit(testFailed > 0)
+end