initialize.m: make string operation compatible with PC

PC systems use a backslash as file separator

src/@dseries/initialize.m

@@ -16,7 +16,11 @@ function initialize(fake)
 % along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
 
 % Get the path to the dseries toolbox.
-dseries_src_root = strrep(which('@dseries/initialize.m'),'@dseries/initialize.m','');
+if ispc()
+    dseries_src_root = strrep(which('@dseries\initialize.m'),'@dseries\initialize.m','');
+else
+    dseries_src_root = strrep(which('@dseries/initialize.m'),'@dseries/initialize.m','');
+end
 
 % Check that the x13 binary is available
 nox13 = false;