Improve the way we test for existence of toolboxes (more reliable in the case...

Improve the way we test for existence of toolboxes (more reliable in the case where the toolbox is installed but not activated)
(cherry picked from commit eabca4c4)

matlab/dynare_config.m

@@ -52,7 +52,7 @@ if ~exist('OCTAVE_VERSION')
     addpath([dynareroot '/missing/rows_columns'])
     % Replacement for vec() (inexistent under MATLAB)
     addpath([dynareroot '/missing/vec'])
-    if isempty(ver('stats'))
+    if ~license('test', 'statistics_toolbox')
         % Replacements for functions of the stats toolbox
         addpath([dynareroot '/missing/stats/'])
     end

matlab/dynare_solve.m

@@ -38,7 +38,7 @@ global options_
 options_ = set_default_option(options_,'solve_algo',2);
 info = 0;
 if options_.solve_algo == 0
-    if ~exist('OCTAVE_VERSION') && isempty(ver('optim'))
+    if ~exist('OCTAVE_VERSION') && ~license('test', 'optimization_toolbox')
         error('You can''t use solve_algo=0 since you don''t have MATLAB''s Optimization Toolbox')
     end
     options=optimset('fsolve');

matlab/solve_one_boundary.m

@@ -225,7 +225,7 @@ for it_=start:incr:finish
                 if (verbose == 1)
                     disp('steady: fsolve');
                 end
-                if exist('OCTAVE_VERSION') || isempty(ver('optim'))
+                if exist('OCTAVE_VERSION') || ~license('test', 'optimization_toolbox')
                     % Note that fsolve() exists under Octave, but has a different syntax
                     % So we fail for the moment under Octave, until we add the corresponding code
                     error('DYNARE_SOLVE: you can''t use solve_algo=0 since you don''t have Matlab''s Optimization Toolbox')