JAV2I13 — Stream encoding for omitted optional custom data

The resolution for issue 3151 does not make it clear how to encode a custom
valuetype that has no optional custom data. This includes custom types
whose writeObject() method calls defaultWriteObject() but writes no additional
data, and custom types that don't write any data at all.

Tihs case could be handled by always writing the org.omg.customRMI.* wrapper
even if there is no data inside of it. However, this is very wasteful of
space. A better approach would be to write a null valuetype (0x00000000) to
indicate the omission of the optional data. The optional data cannot be omitted
entirely, since the receiver would not be able to correctly parse the stream.

Proposed resolution:

Change paragraph "d" in section 1.4.10 from the following:

d. (optional) Additional data written by writeObject, encoded as specified below.
For format version 1, the data is written "as is". For format version 2, the
data is enclosed within a CDR custom valuetype with no codebase and repid
"RMI:org.omg.custom.<class>" where <class> is the fully-qualified name of the
class whose writeObject method is being invoked.

to the following:

d. Additional data written by writeObject, encoded as specified below. For format
version 1, this data is optional and if present must be written "as is". For
format version 2, if optional data is present then it must be enclosed within a
CDR custom valuetype with no codebase and repid "RMI:org.omg.custom.<class>"
where <class> is the fully-qualified name of the class whose writeObject method
is being invoked. For format version 2, if optional data is not present then a
null valuetype (0x00000000) must be written to indicate the absence of optional data.

Closed, accepted. See proposed revised text below