handle undef filename in escape_filename
handle undef internal buttons on input form
handle new Subject dataobj with undef ID
Update postinst.in

Fixed ubuntu config bug in apache2.4, regression tested
Update preinst.in

Added patches for apache 2.4, regression should be fine
Merge pull request #260 from davetaz/master

Updates to debian package builder for apache2.4
Added document_typename_application/vnd.openxmlformats-officedocument.wordprocessingml.document for .docx files.
Typo fixed in XML syntax for document_typename_application/vnd.openxmlformats-officedocument.wordprocessingml.document.
Merge pull request #252 from QUTlib/20140725-handle-undefs

handle undef objects