Batteries user guide : BatNumber.RefOps

`sig type bat__refops_t val ( += ) : BatNumber.RefOps.bat__refops_t Pervasives.ref -> BatNumber.RefOps.bat__refops_t -> unit val ( -= ) : BatNumber.RefOps.bat__refops_t Pervasives.ref -> BatNumber.RefOps.bat__refops_t -> unit val ( *= ) : BatNumber.RefOps.bat__refops_t Pervasives.ref -> BatNumber.RefOps.bat__refops_t -> unit val ( /= ) : BatNumber.RefOps.bat__refops_t Pervasives.ref -> BatNumber.RefOps.bat__refops_t -> unit end`