Resolves: fdo#65583 Elements Dock window needs scroll bar

Based on the patch on Bugzilla by
Marcos Paulo de Souza <marcos.souza.org@gmail.com>

Includes b521c754cba4ef96cf02e0d8913ffcf14fe168d4

Conflicts:
	starmath/source/ElementsDockingWindow.cxx

Change-Id: I215b83894f228b1cc8908f98858b85c8d5378ddb
Reviewed-on: https://gerrit.libreoffice.org/9526
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>