Expose XML_DECL in cmake to give path to xml.dcl
Expose XML_DECL in cmake to give path to xml.dcl

  This exposes XML_DECL to cmake as a user settable option.  This allows
  "make validate" to be used on systems that have xml.dcl in locations
  other than "/usr/share/xml/declaration/xml.dcl".  For example, on Macs
  that have installed OpenSP via MacPorts, the file will be in
  "/opt/local/share/OpenSP/xml.dcl".  This also allows one to specify the
  docbook 4.2 catalog by prepending "-c /path/to/docbook-42.cat " to
  CML_DECL.  It's a little bit of a cheat; the catalog probably get it's
  own cmake variable (or copy it into doc/docbook/src/catalog).
  
  Thanks to David MacMahon for this patch.
  

svn path=/trunk/; revision=10747

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