OutBuffer is now an OutputRange
Merge pull request #2034 from WalterBright/OutBufferToOutputRange

OutBuffer is now an OutputRange
callback uses size_t not double

- Not sure why the curl internal double arguments
  are converted to size_t in the first place though.
Merge pull request #2035 from MartinNowak/fixCurlDocs

callback uses size_t not double