Cleanup and workaround a docbook XSL error:

Cleanup and workaround a docbook XSL error:

* libxslt/xsltproc.c: John Fleck found a typo in usage()
* libxslt/xslt.c: avoid warning if version="1.1" is used
* libxslt/transform.c: forgot to initialize cur->outputFile
* libxslt/functions.c: DOCBOOK_XSL_HACK some versions of DocBook XSL
  use the vendor string to detect supporting chunking, this
  is a workaround to be considered in the list of decent XSLT
  processors <grin/>
Daniel