[R-Forge #5288] fread reads URLs on Linux but not Windows?

Submitted by: Matt Dowle; Assigned to: Nobody; [R-Forge link](https://r-forge.r-project.org/tracker/index.php?func=detail&aid=5288&group_id=240&atid=975)

Raised [here on SO](http://stackoverflow.com/questions/21173293/why-does-fread-not-work-correctly-when-given-url-but-does-from-local-file).
