The old implementation grouped radio buttons if their
object name was the same, and didn't have a groupname property.

The old implementation still works - so that still needs to be
supported, which this patch ensures.

Change-Id: Ied6ddc52d1c4ab5bca56b14da51258460ca2120c
Reviewed-on: https://gerrit.libreoffice.org/62812
Tested-by: Jenkins
Reviewed-by: Justin Luth <justin_luth@sil.org>