- add placeholder to deliver pdftk

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@36394 20353a03-c40f-0410-a6d1-a30d3c3de9de

buildout/software-profiles/pdftk.cfg

+[buildout]
+parts = pdftk
+
+[pdftk]
+url = http://www.pdfhacks.com/pdftk/pdftk-1.41.tar.gz