VS2013: Adjust coinmp to 12.0 vcproj version

Change-Id: I3b069278297c489b0aeb54ebef484c73dee503c0
Reviewed-on: https://gerrit.libreoffice.org/10158
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>