message: Comment out unused private variable in examples/petsc/ex10p.cpp to
  suppress a warning.
diff: @@ -149,13 +149,13 @@ public:
  class PreconditionerFactory : public PetscPreconditionerFactory
  {
  private:
  - const ReducedSystemOperator& op;
  + // const ReducedSystemOperator& op; // unused for now (generates warning)
  public:
  - PreconditionerFactory(const ReducedSystemOperator& op_,
  - const string& name_): PetscPreconditionerFactory(name_), op(op_) {};
  + PreconditionerFactory(const ReducedSystemOperator& op_, const string& name_)
  + : PetscPreconditionerFactory(name_) /* , op(op_) */ {}
  virtual mfem::Solver* NewPreconditioner(const mfem::OperatorHandle&);
  - virtual ~PreconditionerFactory() {};
  + virtual ~PreconditionerFactory() {}
  };
  /** Function representing the elastic energy density for the given hyperelastic
  