and we find that bSplitable in SfxDockingWindow is always true,
ever since

    commit 4bd28a2f
    Date:   Tue Jan 29 15:27:40 2008 +0000
    INTEGRATION: CWS fwk82_SRC680 (1.45.138); FILE MERGED

so we can remove all of the non-splittable code there.
`

Change-Id: Ia7fe607ed02d1a7c69a92bab57e220b19f0e6e87
Reviewed-on: https://gerrit.libreoffice.org/61550
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>