Add Lao breakiterator support for selecting and counting Lao words.

Change-Id: I6da721dc25394dfee12e3028aefbf0546d1be984
Reviewed-on: https://gerrit.libreoffice.org/6669
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>