more fixes:

- added walker for AST_ObjectProperty
- handle redefinitions properly (only mangle one symbol, make them all point
  to a single definition)

DynarchLIB seems to run fine after mangling + compressed output.

lib/ast.js

@@ -136,7 +136,7 @@ var AST_ForIn = DEFNODE("ForIn", "init name object", {
     _walk: function(visitor) {
         return visitor._visit(this, function(){
             if (this.init) this.init._walk(visitor);
-            if (this.name) this.name._walk(visitor);
+            else if (this.name) this.name._walk(visitor);
             if (this.object) this.object._walk(visitor);
             this.body._walk(visitor);
         });
@@ -461,7 +461,13 @@ var AST_Object = DEFNODE("Object", "properties", {
     }
 });
 
-var AST_ObjectProperty = DEFNODE("ObjectProperty", "key value");
+var AST_ObjectProperty = DEFNODE("ObjectProperty", "key value", {
+    _walk: function(visitor) {
+        return visitor._visit(this, function(){
+            this.value._walk(visitor);
+        });
+    }
+});
 
 var AST_ObjectKeyVal = DEFNODE("ObjectKeyval", null, {
 }, AST_ObjectProperty);