swift4: Integer fixes for new integer protocols
swift4: Integer fixes for new integer protocols

- Bitshift operators were moved from FixedWidthInteger to
  BinaryInteger making the _BitShiftable and _IntegerLike
  protocols incorrect.

- Remove _BitShiftable and _IntegerLike and just use
  FixedWidthInteger for constraining the return type
  of scan() and scanHex().

johnno1962e/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,parkera/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,alblue/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,parkera/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,e78l/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,parkera/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,apple/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,apple/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,alblue/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation,apple/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,apple/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,alblue/swift-corelibs-foundation,e78l/swift-corelibs-foundation,e78l/swift-corelibs-foundation,alblue/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,e78l/swift-corelibs-foundation,alblue/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,apple/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,johnno1962e/swift-corelibs-foundation