fdo#73147 add Excel2010 functions NETWORKDAYS.INTL and WORKDAY.INTL

Change-Id: I3ab9dde5c421a3a3e6022a27be37f23547197317
Reviewed-on: https://gerrit.libreoffice.org/8772
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>