Export of image/files fails if page name too long

If the page names of documents where attachments are stored are too long, the export fails to save those attachments and export them properly in the zip (for the html export) or to insert images in the pdf, if the image attachments are not public.

We need to use a hashcode for the attachments file names.

java.io.FileNotFoundException: /usr/local/apache-tomcat-6.0.18/work/Catalina/localhost/xwiki/Hn0dIGgH/Design.Validation Principles Enterprise Solutions for Microsoft Exchange Server 2007 CLARiiON CX3-80 Local and Remote Data Protection for Exchange Server 2007 Enabled by RecoverPoint CRR and Replication Manager-Environment architecture.output_html_6c2059af.jpg (File name too long)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(Unknown Source)
at java.io.FileOutputStream.<init>(Unknown Source)
at com.xpn.xwiki.pdf.impl.PdfURLFactory.createAttachmentURL(PdfURLFactory.java:51)
at com.xpn.xwiki.doc.XWikiDocument.getAttachmentURL(XWikiDocument.java:952)
at com.xpn.xwiki.XWiki.getAttachmentURL(XWiki.java:4514)