Default CBOR reader implementation causes closures saved in class members to error

[JohnathonNow]

minilang/src/ml_cbor.c

Line 414 in 3cbfc4c

value_handler(Reader, MLNil);

Write now if you serialize a class instance who has a member who is a closure, when you de-serialize it, undefineds become nulls, leading to errors. I recommend SIMPLE_UNDEFINEDs being MLBlank instead of MLNils.

[rajamukherji]

It might be better to add a new type (probably called "undefined" or "unknown") so the resulting error message is clearer.
In general though, closures in instances should be CBOR encoded properly. I did a simple test and it does work. So I wonder if there's a specific value referenced in the closure that isn't serializable leading to an error?

[rajamukherji]

MLBlank is used for serializing partial functions so I've added a new "unknown" type (MLUnknown) for this situation, in dev ready for testing.