EnumGroup findEnumGroupReference(String fullRefName, String enclosingNamespace)
    {
        HasName refObj = findReference(fullRefName, enclosingNamespace);
        if (refObj instanceof EnumGroup)
            return (EnumGroup) refObj;
        else
            return null;
    }
Given the name of a Message/EnumGroup reference and the namespace enclosing that reference (can be a full message
name or package name), returns the referenced object if it exists.

@param fullRefName
           The full name of the object as specified by the reference, including a package name if it was
           specified
@param fullEnclosingNamespace
           The full enclosing namespace of the reference
@return A Message or EnumGroup instance, or null
protostuff-parser/src/main/java/io/protostuff/parser/Proto.java