* Add and use TValueSign

packages/rtl/math.pas

@@ -57,13 +57,16 @@ function randg(mean,stddev : float) : float;
 function RandomRange(const aFrom, aTo: Integer): Integer;
 function RandomRange(const aFrom, aTo: NativeLargeInt): NativeLargeInt;
 
+Type
+  TValueSign = -1..1;
+
 const
   NegativeValue = -1;
   ZeroValue = 0;
   PositiveValue = 1;
 
-function Sign(const AValue: Integer): Integer; external name 'Math.sign'; overload;
-function Sign(const AValue: Double): Double; external name 'Math.sign'; overload;
+function Sign(const AValue: Integer): TValueSign; external name 'Math.sign'; overload;
+function Sign(const AValue: Double): TValueSign; external name 'Math.sign'; overload;
 
 function IsZero(const d: Double; Epsilon: Double): Boolean; overload;
 function IsZero(const d: Double): Boolean; overload;