Add a missing virtual destructor on Mesh
Add a missing virtual destructor on Mesh

liangjg/openmc,amandalund/openmc,liangjg/openmc,mit-crpg/openmc,paulromano/openmc,smharper/openmc,liangjg/openmc,mit-crpg/openmc,paulromano/openmc,liangjg/openmc,amandalund/openmc,shikhar413/openmc,amandalund/openmc,smharper/openmc,smharper/openmc,mit-crpg/openmc,walshjon/openmc,walshjon/openmc,amandalund/openmc,walshjon/openmc,shikhar413/openmc,mit-crpg/openmc,smharper/openmc,walshjon/openmc,shikhar413/openmc,paulromano/openmc,paulromano/openmc,shikhar413/openmc