-unexported flag encodes/decodes unexported fields

[zeldovich]

The documentation for msgp -unexported says that it will process unexported types (like type myint int), but it has the unexpected additional behavior of encoding and decoding unexported fields (like type Foo struct { hidden int }). This can be a significant change in behavior in scenarios where the developer was expecting unexported fields to be hidden at encoding time and to be preserved at decoding time.

It would be great to reconcile the documentation with behavior of -unexported, ideally by not encoding/decoding unexported struct fields.

[philhofer]

I agree the docs should be changed. I'll also add this to the list of warts to be addressed for version 2.