Seems like Microsoft recently updated the Database Software support for Lync Server 2013 to include Failover clustering as a supported Database high availability solution in addition to SQL
We can directly notice that SQL failover Clustering support has been introduced without the need to apply any Server side updates. which confirm that this recent statement is the result of the extensive tests applied by Microsoft and the clients that participated in the testing program.
it is good to note that active passive failover clustering is only supported, so I believe that doesn’t include SQL always on availability groups.
For my opinion this is another important update introduced to Lync sever 2013 product which will be most welcomed by database administrators, which doesn’t encourage using SQL mirroring and also in organizations where SQL consolidations are a required.