Use the suggested filename ("Content-Disposition: filename" HTTP header) also when using
the kioexec mechanism (download to tempfile and open in non-url-aware application).
This makes the name of the tempfile slightly nicer, but more importantly it allows
some applications to understand the type of file being given to them (e.g. "foo.doc" for openoffice)
Bug report, test, and some improvements to the patch by Andre Woebbeking.