[Libreoffice] Fix for fdo#35543

Hi,

I commited a fix for fdo#35543 (FILEOPEN: hangs when trying to open
SpreadsheetML). The fix is actually more of a workaround than a real
fix, because it simply adds a timeout with the ability to retry or abort
an ongoing load request to the xsltfilter module. I tested the fix on
master but would be glad if someone would take a look at it and see if
there's anything stupid going on there.

The main difference is that we're now waiting until the whole input file
has been transformed and only then start to parse it, which might make a
performance difference for very large files (which should be negligible
compared to the time spent in the xslt processor).

Bug:
https://bugs.freedesktop.org/show_bug.cgi?id=35543

Fix:
http://cgit.freedesktop.org/libreoffice/filters/commit/?id=2e9f9d82110342601d28408ae77d63b673993ebe

Thanks a lot,

Peter