math/rand: add a comment for the i=0 iteration
math/rand: add a comment for the i=0 iteration

Fixes #13215

Change-Id: I126117d42e7c1e69cbc7fad0760e225b03ed15bd
Reviewed-on: https://go-review.googlesource.com/16852
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

codestation/go,Endika/go,mwhudson/go,Jordanzuo/go,golang/go,derekmarcotte/go,theif519/go,cloudflare/go,Samurais/go,Endika/go,deft-code/go,Endika/go,theif519/go,linux-on-ibm-z/go,4ad/go,odeke-em/go,CAFxX/go,nawawi/go,derekmarcotte/go,sndnvaps/go,akutz/go,ImJasonH/go,Endika/go,nawawi/go,josharian/go,akutz/go,Cofyc/go,theif519/go,derekmarcotte/go,golang/go,vsekhar/elastic-go,goodlang/good,josharian/go,momchil-velikov/go,sndnvaps/go,Cofyc/go,4ad/go,CAFxX/go,codestation/go,vanloswang/go,josharian/go,4ad/go,kim-racktop/go,josharian/go,cloudflare/go,miolini/go,deft-code/go,deft-code/go,roth1002/go,sndnvaps/go,ImJasonH/go,mwhudson/go,sndnvaps/go,fjballest/golang,4ad/go,codestation/go,cloudflare/go,mwhudson/go,Jordanzuo/go,suncycheng/go,miolini/go,Endika/go,cloudflare/go,derekmarcotte/go,polyverse-security/go,Endika/go,vsekhar/elastic-go,fjballest/golang,odeke-em/go,ganboing/go-esx,ganboing/go-esx,Endika/go,josharian/go,akutz/go,kim-racktop/go,sndnvaps/go,momchil-velikov/go,binarycrusader/go,deft-code/go,golang/go,cyberroadie/go,goodlang/good,polyverse-security/go,ImJasonH/go,linux-on-ibm-z/go,derekmarcotte/go,sndnvaps/go,theif519/go,Jordanzuo/go,deft-code/go,CAFxX/go,mwhudson/go,CAFxX/go,polyverse-security/go,vsekhar/elastic-go,nawawi/go,odeke-em/go,akutz/go,Cofyc/go,kim-racktop/go,kim-racktop/go,momchil-velikov/go,vanloswang/go,theif519/go,4ad/go,cyberroadie/go,goodlang/good,nawawi/go,vanloswang/go,codestation/go,polyverse-security/go,ImJasonH/go,ganboing/go-esx,cyberroadie/go,josharian/go,vsekhar/elastic-go,derekmarcotte/go,Jordanzuo/go,roth1002/go,Cofyc/go,roth1002/go,CAFxX/go,akutz/go,Cofyc/go,codestation/go,miolini/go,roth1002/go,momchil-velikov/go,cloudflare/go,nawawi/go,momchil-velikov/go,suncycheng/go,CAFxX/go,christopher-henderson/Go,roth1002/go,golang/go,cyberroadie/go,linux-on-ibm-z/go,4ad/go,momchil-velikov/go,theif519/go,miolini/go,nawawi/go,polyverse-security/go,linux-on-ibm-z/go,vsekhar/elastic-go,fjballest/golang,suncycheng/go,Samurais/go,goodlang/good,odeke-em/go,vanloswang/go,odeke-em/go,Jordanzuo/go,sndnvaps/go,codestation/go,goodlang/good,cloudflare/go,binarycrusader/go,Samurais/go,akutz/go,Cofyc/go,linux-on-ibm-z/go,suncycheng/go,binarycrusader/go,golang/go,miolini/go,suncycheng/go,ganboing/go-esx,derekmarcotte/go,suncycheng/go,polyverse-security/go,4ad/go,Samurais/go,cloudflare/go,josharian/go,ganboing/go-esx,momchil-velikov/go,polyverse-security/go,vanloswang/go,odeke-em/go,Samurais/go,CAFxX/go,linux-on-ibm-z/go,miolini/go,akutz/go,CAFxX/go,vsekhar/elastic-go,miolini/go,mwhudson/go,mwhudson/go,cyberroadie/go,suncycheng/go,Samurais/go,cyberroadie/go,kim-racktop/go,goodlang/good,mwhudson/go,kim-racktop/go,ganboing/go-esx,vsekhar/elastic-go,polyverse-security/go,vsekhar/elastic-go,roth1002/go,Jordanzuo/go,theif519/go,sndnvaps/go,momchil-velikov/go,binarycrusader/go,cyberroadie/go,ganboing/go-esx,goodlang/good,fjballest/golang,fjballest/golang,cloudflare/go,Jordanzuo/go,nawawi/go,deft-code/go,linux-on-ibm-z/go,binarycrusader/go,deft-code/go,Jordanzuo/go,ImJasonH/go,codestation/go,derekmarcotte/go,fjballest/golang,Cofyc/go,roth1002/go,binarycrusader/go,codestation/go,odeke-em/go,kim-racktop/go,kim-racktop/go,golang/go,vanloswang/go,roth1002/go,4ad/go,vanloswang/go,fjballest/golang,fjballest/golang,Samurais/go,vanloswang/go,deft-code/go,ImJasonH/go,nawawi/go,ganboing/go-esx,cyberroadie/go,Endika/go,ImJasonH/go,goodlang/good,golang/go,josharian/go,binarycrusader/go,Samurais/go,golang/go,binarycrusader/go,akutz/go,suncycheng/go,ImJasonH/go,linux-on-ibm-z/go,miolini/go,odeke-em/go,theif519/go,mwhudson/go,Cofyc/go