Production 64 in the November spec.

I think we should removed the well-formed check/constraint on
requiring entities to be declared. Let's take the following document
as an example:

    <?XML VERSION="1.0">

It seems to me that requiring that entities be declared doesn't buy a
whole lot. In the worste case, you might just have some peices
missing, but what *remains* is still well-formed. 

Also, for most external entities, you could still search for them
based on the name of the entity:

   ENTITY "foo" "http://foo.com/foo.sgml"
   ENTITY "bar" "http://bar.com/bar.sgml"

and with protocol labelling, still discern the type/notation of the
data as well as any NDATA declaration could give you. You could
also have other application behaviour to resolve entities.