Remove unused variable 'kAFStreamToStreamBufferSize'
Don't use NSUInteger as format argument, add explicit cast instead
Merge pull request #1764 from doo/ake-fix-warnings

Fix two warnings that show up recently
Merge remote-tracking branch 'afnetworking/1.x' into 1.x

* afnetworking/1.x:
  Don't use NSUInteger as format argument, add explicit cast instead
  Remove unused variable 'kAFStreamToStreamBufferSize'