Issue Description:

In particular case, Swift 3.1 compiler generates warning of global math function like this:

abs.swift:4:12: warning: 'abs' is deprecated: Please use the `abs(_:)` free function

Entire code is like this:

abs.swift

extension Double {

  func myAbsolute(value : Double) -> Double {
    return abs(value)
  }

  static func myStaticAbsolute(value : Double) -> Double {
    return abs(value)
  }

}

func myAbsolute(value: Double) -> Double {
  return abs(value)
}

First function (non-static one) does not produce any warning but second one (static one) does produce the warning. The last function (defined in global space) dose not produce any warnings.

The code can be compiled without any warning prior to swift 3.1.