message: Add unary + operator to AutoSIMD
diff: @@ -117,6 +117,11 @@ struct MFEM_AUTOSIMD_ALIGN__ AutoSIMD
  return r;
  }
  + inline MFEM_ALWAYS_INLINE AutoSIMD operator+() const
  + {
  + return *this;
  + }
  +
  inline MFEM_ALWAYS_INLINE AutoSIMD operator+(const AutoSIMD &v) const
  {
  AutoSIMD r;
  