... attribute in anchor elements.

I used Svggnode class a a reference for this.

Change-Id: Id2a58bd913f9984dc91163ca0f333c016aa981f1
Reviewed-on: https://gerrit.libreoffice.org/22822Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Xisco Faulí <anistenis@gmail.com>