handle 'unset' as a CSS-wide identifier the same way as initial (Fixes w3c#107)

Author: ylafon

org/w3c/css/parser/CssPropertyFactory.java

@@ -227,10 +227,11 @@ public synchronized CssProperty createProperty(ApplContext ac, AtRule atRule, St
 		}
 
 		CssIdent initial = CssIdent.getIdent("initial");
+        CssIdent unset = CssIdent.getIdent("unset");
 
 		try {
 			if ((ac.getCssVersion().compareTo(CssVersion.CSS3) >= 0) && (expression.getCount() == 1)
-					&& expression.getValue().equals(initial)) {
+					&& (expression.getValue().equals(initial) || expression.getValue().equals(unset))) {
 				// create an instance of your property class
 				Class[] parametersType = {};
 				Constructor constructor = Class.forName(classname).getConstructor(parametersType);

org/w3c/css/properties/css/CssProperty.java

@@ -92,12 +92,14 @@ public abstract class CssProperty
     public static final CssIdent initial;
     public static final CssIdent none;
     public static final CssIdent currentColor;
+    public static final CssIdent unset;
 
     static {
         inherit = CssIdent.getIdent("inherit");
         transparent = CssIdent.getIdent("transparent");
         initial = CssIdent.getIdent("initial");
         none = CssIdent.getIdent("none");
+        unset = CssIdent.getIdent("unset");
         currentColor = CssIdent.getIdent("currentColor");
     }