JuliaLang/julia — pull request #3542 by daviddelaat (2013-06-26 20:29:42+00:00)
Title: add general copysign method

I noticed that
```
int(BigInt(3) // BigInt(5))
```
doesn't work due to there being no `copysign` method for `BigInt`.

I didn't really see a reason not to implement this for general `Real` arguments; I hope that's ok.