ACTION-684: to add a version of http://www.w3.org/2005/rules/wiki/RDF_Combination_Constant_Equivalence_2 with the import having a ^^xs:string

Done. See:
http://www.w3.org/2005/rules/wiki/RDF_Combination_Constant_Equivalence_4

-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
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No one who cannot rejoice in the discovery of
his own mistakes deserves to be called a
scholar.
  - Donald Foster