I2JAV11 — Any extract operations for tk_abstract_interface

It is not clear from the IDL to Java language mapping spec whether a
valuetype or object reference can be inserted into an "any" whose TypeCode is
tk_abstract_interface. Neither is it clear whether a valuetype or object
reference that has been passed across the wire inside an "any" with a
tk_abstract_interface TypeCode can be extracted using the normal extract
operations for valuetype or object reference.

Proposed resolution:

Add the following text to section 1.16:

An object reference can be inserted into an "any" that has a matching tk_objref
TypeCode. If the object reference inherits from an abstract interface, then
it can also be inserted into an "any" that has a matching tk_abstract_interface
TypeCode. A nil object reference can be inserted into any "any" that has
a tk_objref or tk_abstract_interface TypeCode.

A valuetype can be inserted into an "any" that has a matching tk_value or
tk_value_box TypeCode. If the valuetype supports an abstract interface, then
it can also be inserted into an "any" that has a matching tk_abstract_interface
TypeCode. A null valuetype can be inserted into any "any" that has a tk_value,
tk_value_box, or tk_abstract_interface TypeCode.

The extract_Object operation can be used to extract an object reference
(including a nil object reference) from an "any" that has a TypeCode of tk_objref.
It can also be used to extract an object reference (including a nil object
reference) from an "any" that has a TypeCode of tk_abstract_interface and a
boolean discriminator of true.

The extract_Value operation can be used to extract a valuetype (including a
null valuetype) from an "any" that has a TypeCode of tk_value or tk_value_box.
It can also be used to extract a valuetype (including a null valuetype) from
an "any" that has a TypeCode of tk_abstract_interface and a boolean discriminator
of false.

Incorporate changes from Simon's proposal and close issue