Update MetaPhysicL
Update MetaPhysicL

This incorporates a compiler warning fix from Alex, plus a workaround
for clang 9 problems from me.

jwpeterson/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,dschwen/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,libMesh/libmesh,libMesh/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,libMesh/libmesh,dschwen/libmesh,dschwen/libmesh,dschwen/libmesh,libMesh/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,jwpeterson/libmesh,libMesh/libmesh,libMesh/libmesh