Automatic forcing of promises in Klink (addendum)
I had meant to explain also about auto-forcing in `$let' or `$define!', but for some reason I didn't. So I'm adding this now.
Background: In Kernel, combiners like `$let' and `$define!' destructure values. That is, they define not just one thing, but an arbitrarily detailed tree of definiendums.
So when a value doesn't match the tree of definiendums, or only partly matches, but the part that doesn't match is a promise, Klink forces the promise and tries the match again.
Unlike argobject destructuring, this doesn't check type.