Document crosslinks

I am just preparing the LC candidate for concepts.

I will follow Frank's example on the cross links,and use cross links to 
shadow TR space where I expect a link to the LC2 doc. All other links 
(particularly dated links to earler versions of concepts) should not be 
processed.


I note that syntax has not followed this, but the links still need 
processing with an algorithm like:

For each doc1 in collection
   If doc1 != syntax
       patch links to doc1 in syntax

The dated links to syntax within syntax should not be patched.

Jeremy