Add new basic function: spline2

source/carbon/carbon_model_to_core_fun_kit.f90

@@ -41,8 +41,8 @@ contains
                 fun_kit%fun => fun_mm
             case('step')
                 fun_kit%fun => fun_step
-            !case('spline')
-                !fun_kit%fun => fun_spline
+            case('spline')
+                fun_kit%fun => fun_spline
             case default
                 stop "check failed : unknown funtype at set_fun"
         end select