[SVG2] Add support for the 'turn' unit in <angle>.

Source/core/svg/SVGAngle.idl

 /*
  * Copyright (C) 2004, 2005 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  * Copyright (C) 2006 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 13 matching lines @@
     ImplementedAs=SVGAngleTearOff,
     SetWrapperReferenceTo(SVGElement contextElement),
     TypeChecking=Interface|Nullable,
 ] interface SVGAngle {
     // Angle Unit Types
     const unsigned short SVG_ANGLETYPE_UNKNOWN = 0;
     const unsigned short SVG_ANGLETYPE_UNSPECIFIED = 1;
     const unsigned short SVG_ANGLETYPE_DEG = 2;
     const unsigned short SVG_ANGLETYPE_RAD = 3;
     const unsigned short SVG_ANGLETYPE_GRAD = 4;
+    const unsigned short SVG_ANGLETYPE_TURN = 5;
 
     readonly attribute unsigned short unitType;
     [RaisesException=Setter] attribute float value;
     [RaisesException=Setter] attribute float valueInSpecifiedUnits;
 
     [TreatNullAs=NullString, RaisesException=Setter] attribute DOMString valueAsString;
 
     [RaisesException] void newValueSpecifiedUnits(unsigned short unitType, float valueInSpecifiedUnits);
 
     [RaisesException] void convertToSpecifiedUnits(unsigned short unitType);
 };