Change default platform to something that don't change when it isn't nee...

...ded.

News.txt
- Better default compiledir name

@lamblin and @abergeron can both of you review comment on this before? Currently the compiledir change too often. I think that this version would work on windows and mac. I'll test on windows. @abergeron can you test on mac?
`len(sp) > 2` would also be fine on Mac.