[BUGFIX] Remove space between buttons in button-group

Hide the whitespace between buttons in button groups.

Releases: master
Resolves: #65110
Change-Id: I250fb1958d5056a9da0078fc6499f047d68aba1d
Reviewed-on: http://review.typo3.org/36993


Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>