[BUGFIX] IE9 compatibility clear cache menu

The prototype library shipped with TYPO3 is not compatible with IE9
anymore. Since prototype will be replaced in the near future the easiest
solution is to use plain JavaScript.

Change-Id: I1dc732a61531fa585ed8e0ba6ce8df1b23f3b8bd
Resolves: #36364
Releases: 6.1, 6.0, 4.7, 4.6, 4.5
Reviewed-on: https://review.typo3.org/17971
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert