Foundation: more idiomatic Swift in NSKeyedUnarchiver

Unwrapped variable can have same name as optional.

Author: lhoward

Sources/Foundation/NSKeyedUnarchiver.swift

@@ -311,14 +311,14 @@ open class NSKeyedUnarchiver : NSCoder {
             return aClass
         }
 
-        guard let unwrappedClassDict = classDict else {
+        guard let classDict = classDict else {
             return false
         }
 
         // TODO is it required to validate the superclass hierarchy?
-        let assertedClassName = unwrappedClassDict["$classname"] as? String
-        let assertedClassHints = unwrappedClassDict["$classhints"] as? [String]
-        let assertedClasses = unwrappedClassDict["$classes"] as? [String]
+        let assertedClassName = classDict["$classname"] as? String
+        let assertedClassHints = classDict["$classhints"] as? [String]
+        let assertedClasses = classDict["$classes"] as? [String]
 
         if let assertedClassName = assertedClassName {
             let assertedClass : AnyClass? = _classForClassName(assertedClassName)