[XeTeX] Issue with CJK in pdf build

[Chris Jones]

Hmm.. the attached unicode.xml DocBook file should have <screen>
</screen> tags rather than <para> </para> delimiting the 'Unicode
samples'. 

I forgot I had modified it to try and get rid of some of the errors.

All the same, whatever the input, I think I'm getting more error
messages than I bargained for and the final .pdf does not get built in
either case.

CJ