message: ENH: short-circuit logic when mesh is watertight
  Adds short-circuit logic for when the mesh is watertight.
  Instead of evaluating whether a cell is on a boundary by
  looking at its constituent faces,  the code now memsets
  the boundary flag to "0".
diff: @@ -264,6 +264,14 @@ WatertightStatus isSurfaceMeshWatertight( UMesh* surface_mesh )
  }
  } // END for all faces
  + if ( retval == WatertightStatus::WATERTIGHT )
  + {
  + /* short-circuit */
  + const IndexType numCells = surface_mesh->getNumberOfCells();
  + std::memset( boundary, INTERNAL, sizeof(int)*numCells );
  + return retval;
  + }
  +
  // Mark boundary cells
  const IndexType numCells = surface_mesh->getNumberOfCells();
  for ( IndexType icell=0; icell < numCells; ++icell )
  