NSCoder: implement NSSecureCoding stub

Implement stubs for NSSecureCoding which do not break projects that rely
on it.

Source/NSCoder.m

@@ -35,6 +35,7 @@
 #define	EXPOSE_NSCoder_IVARS	1
 #import "Foundation/NSData.h"
 #import "Foundation/NSCoder.h"
+#import "Foundation/NSSet.h"
 #import "Foundation/NSSerialization.h"
 #import "Foundation/NSUserDefaults.h"
 
@@ -331,6 +332,17 @@ static unsigned	systemVersion = MAX_SUPPORTED_SYSTEM_VERSION;
 
 // Keyed archiving extensions
 
+- (BOOL) requiresSecureCoding
+{
+  [self subclassResponsibility: _cmd];
+  return NO;
+}
+
+- (void) setRequiresSecureCoding: (BOOL)secure
+{
+  [self subclassResponsibility: _cmd];
+}
+
 - (BOOL) allowsKeyedCoding
 {
   return NO;
@@ -397,6 +409,18 @@ static unsigned	systemVersion = MAX_SUPPORTED_SYSTEM_VERSION;
   return nil;
 }
 
+- (id) decodeObjectOfClass: (Class)cls forKey: (NSString *)aKey
+{
+  return [self decodeObjectOfClasses: [NSSet setWithObject:(id)cls]
+			      forKey: aKey];
+}
+
+- (id) decodeObjectOfClasses: (NSSet *)classes forKey: (NSString *)aKey
+{
+  [self subclassResponsibility: _cmd];
+  return nil;
+}
+
 - (void) encodeBool: (BOOL) aBool forKey: (NSString*)aKey
 {
   [self subclassResponsibility: _cmd];

Source/NSKeyedUnarchiver.m

@@ -365,6 +365,16 @@ static NSMapTable	*globalClassMap = 0;
   return YES;
 }
 
+- (BOOL)requiresSecureCoding
+{
+  return NO;
+}
+
+- (void)setRequiresSecureCoding: (BOOL)secure
+{
+  return;
+}
+
 - (Class) classForClassName: (NSString*)aString
 {
   return _clsMap == 0 ? Nil : (Class)NSMapGet(_clsMap, (void*)aString);
@@ -636,6 +646,11 @@ static NSMapTable	*globalClassMap = 0;
   return nil;
 }
 
+- (id) decodeObjectOfClasses: (NSSet *)classes forKey: (NSString *)key
+{
+  return [self decodeObjectForKey: key];
+}
+
 - (NSPoint) decodePoint
 {
   NSPoint	p;