lang: No need to set prototype for Lang.Interface
lang: No need to set prototype for Lang.Interface

Since we are removing any direct alterations of objects' prototypes, we
can remove this one altogether as it turns out that it isn't necessary.

The normal way to create an object with a custom prototype is
Object.create(), and since it's not necessary for the interface object to
be callable, we don't have to do the trick where we give a function a
custom prototype.

We still need to do the trick for GObject interfaces, because the
interface object needs to be the object returned from
Gi.register_interface().

https://bugzilla.gnome.org/show_bug.cgi?id=751252

endlessm/gjs,endlessm/gjs,endlessm/gjs,endlessm/gjs,endlessm/gjs