proposal: math/big: Rat.SetUint64

[TuomLarsen]

Please consider adding Rat.SetUint64 in addition to Rat.SetInt64 as there is currently no way of setting by uint64 integers. This is similar to Int.SetInt64 and Int.SetUint64.

[rsc]

Go 1 had Rat.SetInt64 and Int.SetInt64, but then Go 1.1 added Int.SetUint64. At the time we clearly forgot about Rat. This seems fine, and @griesemer agrees.

[gopherbot]

Change https://golang.org/cl/160682 mentions this issue: math/big: implement Rat.SetUint64

[TuomLarsen]

Thank you!