[FEATURE] RequireJS module for split buttons

A new RequireJS module for split button handling has been added.

Resolves: #70531
Releases: master
Change-Id: I4a1b0386df2fa00e317f5d602df0701661fdda84
Reviewed-on: http://review.typo3.org/43928


Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>