moretypes: remove reference to math.Pow (it's meant to be xor)
moretypes: remove reference to math.Pow (it's meant to be xor)

Fixes golang/go#11231

Change-Id: Id2d85520d18bc42c1c08061a2f98a88255e6adf8
Reviewed-on: https://go-review.googlesource.com/11134
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

raindev/tour,scryner/tour,Jasperste/tour,shuLhan/tour,shuLhan/tour,raindev/tour,dupoxy/go-tour-fr,campoy/go-tour-ua,scryner/tour,Go-zh/tour,LaPingvino/go-tour-nl,zorion/go-tour-ca,LaPingvino/go-tour-eo,tamnd/tour,Jasperste/tour,bbandaru/tour,dupoxy/go-tour-fr,tamnd/tour,LaPingvino/go-tour-nl,raindev/tour,zorion/go-tour-ca,shuLhan/tour,scryner/tour,campoy/go-tour-ua,LaPingvino/go-tour-nl,tamnd/tour,golians/tour,shuLhan/go-tour-id,Go-zh/tour,dupoxy/go-tour-fr,golang/tour,golians/tour,phoorichet/tour,bbandaru/tour,Jasperste/tour,phoorichet/tour,LaPingvino/go-tour-eo,bbandaru/tour,shuLhan/go-tour-id,campoy/go-tour-ua,golians/tour,Go-zh/tour,shuLhan/go-tour-id,phoorichet/tour,scryner/tour,Go-zh/tour,LaPingvino/go-tour-eo