* Implement ID/IDREF support for xml files which use external DTD files in   the DOCTTYPE definitions. Due to some pecularities in the libxml2 SAX   handlers we had to load this DTD 'by hand'.   NOTE: when using these DOCTYPE definitions with ID/IDREFS the performance   of the shredder will be influenced because in this case for every encountered   attribute its properties have to be checked.   BUG: when using filenames these DTD filenames should be absolute. DTD URL's   work OK.
* Implement ID/IDREF support for xml files which use external DTD files in
  the DOCTTYPE definitions. Due to some pecularities in the libxml2 SAX
  handlers we had to load this DTD 'by hand'.
  NOTE: when using these DOCTYPE definitions with ID/IDREFS the performance
  of the shredder will be influenced because in this case for every encountered
  attribute its properties have to be checked.
  BUG: when using filenames these DTD filenames should be absolute. DTD URL's
  work OK.

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb