Added comment warning for Particle::Bank struct defintion that changes to it must also be made in MPI type declaration.
Added comment warning for Particle::Bank struct defintion that changes to it must also be made in MPI type declaration.

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