Map 'cmn' Mandarin Chinese with associated country for Simplified
and Traditional to the technically used 'zh' macrolanguage code.

Change-Id: Ifb8a31e728bbf828f13145513bc56a51684ea134
Reviewed-on: https://gerrit.libreoffice.org/73563
Tested-by: Jenkins
Reviewed-by: Eike Rathke <erack@redhat.com>