call renpy.const for stores marked with _constant = True

[Elckarow]

since constant stores aren't supposed to change, let's use that for screen optimization

[renpytom]

I'm not convinced that this is correct, and I need to think about it a bit more. (It's quite possible that _constant is misnamed, and it's more propertly _do_not_rollback.) This may be fixable, but I want to think about this before committing to this change.

[mal]

At least as I understand it, calling renpy.const with the module names wouldn't be beneficial anyway as the whole name (as it would appear in screens) needs to be declared. i.e. renpy.const('renpy.foo') isn't going to result in renpy.foo.bar being treated as const.

edit: TIL. For future readers, see the post below.

[Elckarow]

renpy.const('renpy.foo') isn't going to result in renpy.foo.bar being treated as const.

it does treat it as const.

[Gouvernathor]

About what Tom said : it's currently documented as being related to constantness, and we offer no guarantee about rolling back. In particular, the annoying question of an object accessed both through define and default, would rise again for an object present in that store but also reachable from a rollbackable object. It would rise if we start documenting it that way.
I think we should expand on the way to constantness.