TYPO3 Core

Problem:
Different application offers to possibility to save images as ".tiff" including the screenshot tool in Mac OSX. It's not possible to use this image extension in TYPO3 without adding it to the imagefile_ext in the install tool

Solution:
This format should also be able to use in TYPO3, without having to add it in the install tool, therefore it's added to the array in t3lib/config_default.php

(issue imported from #M14027)