[BUGFIX] CSV-Download not working in IE and HTTPS backend

When using a HTTPS backend the download of CSV is not
working in Internet Explorer browser versions lower then 9.
Add the needed header to fix this problem.

Change-Id: Iefa63fb37d57491fb73bfd504b6caed5b76c8cac
Resolves: #16491
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Reviewed-on: https://review.typo3.org/27481
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn