[TASK] Use autoprefixer

Add postcss to run autoprefixer for
- last two browser generations
- Firefox ESR
- IE 9

This will drop vendor prefixes for browsers that are unsupported
with TYPO3 CMS (mostly IE 8 only) and vice versa.

Resolves: #70150
Releases: master
Change-Id: I2a4e02e3d57de7b682ca089e4d91dd1a071efc87
Reviewed-on: http://review.typo3.org/43610


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>