feat(sp_resource): impure elmetal free() binding

Author: rouson

example/user_object_smart_pointer.f90

@@ -26,7 +26,7 @@ module function construct(user_object) result(user_object_ptr)
 
   interface
 
-    module subroutine free(self)
+    impure elemental module subroutine free(self)
       implicit none
       class(user_object_ptr_t), intent(inout) :: self
     end subroutine

src/smart_pointer/sp_resource_m.f90

@@ -11,7 +11,7 @@ module sp_resource_m
 
   abstract interface
 
-    subroutine free_interface(self)
+    impure elemental subroutine free_interface(self)
       import sp_resource_t
       class(sp_resource_t), intent(inout) :: self
     end subroutine