[CCC][stdlib] FloatingPoint should refine AbsoluteValuable for compatibility

Author: Max Moiseev

stdlib/public/core/FloatingPoint.swift.gyb

@@ -167,7 +167,7 @@ word_bits = int(CMAKE_SIZEOF_VOID_P) * 8
 ///     print("Average: \(average)°F in \(validTemps.count) " +
 ///           "out of \(tempsFahrenheit.count) observations.")
 ///     // Prints "Average: 74.84°F in 5 out of 7 observations."
-public protocol FloatingPoint: Comparable, Arithmetic,
+public protocol FloatingPoint: Comparable, Arithmetic, AbsoluteValuable,
   SignedNumber, Strideable {
 
   /// A type that represents any written exponent.