Tweaks to avoid compiler warnings with gcc-4

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@21390 72102866-910b-0410-8b05-ffd578937521

Source/NSNotification.m

@@ -29,6 +29,10 @@
 #include "Foundation/NSCoder.h"
 #include "Foundation/NSString.h"
 
+@class	GSNotification;
+@interface GSNotification : NSObject	// Help the compiler
+@end
+
 /**
  *  <p>Represents a notification for posting to an [NSNotificationCenter].
  *  Consists of a name, an object, and an optional dictionary.  The
@@ -43,9 +47,7 @@
 static Class	abstractClass = 0;
 static Class	concreteClass = 0;
 
-@class	GSNotification;
-
-+ (NSNotification*) allocWithZone: (NSZone*)z
++ (id) allocWithZone: (NSZone*)z
 {
   if (self == abstractClass)
     {