[developers] serious preprocessor bug

[Ben Waldron]

Oops. I've checked in a fix for this bug.

- Ben

Ann Copestake wrote:
> the preprocessor with the latest LKB revision appears to be `pruning' 
> tokens corresponding to words which occur more than once in an input.  
> A warning message appears
> ~&WARNING: pruning duplicate edge - apparently from the 
> get-duplicate-edge-sets function in saf2.lsp
>  
> Ann
>  
> PS just using this account because I can't access my usual one today.  
> Please don't reply to this address.