[TASK] Reduce file size of core images

Reduce the file size without losing quality.
This reduces total typo3 directory size by ~2 MB.

Change-Id: I56d1e9eccee05833a4e0373211eaeb3fefbc4336
Resolves: #58110
Releases: 6.3
Reviewed-on: http://review.typo3.org/29829


Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>