CORBA35 — Default constructor for Java values

Summary: The OBV spec is not very clear about whether the Java class
generated for an IDL value has a default (no-argument) constructor.

A no-argument constructor is needed so that the Helper class
can construct a value when demarshalling. However, it should be
package-private in order to limit its visbility to the Helper
class and not expose it to client code. This is also true for
state fields declared as private in the IDL value type (which the
spec currently states are mapped to private in Java).