macosx: fixed compilation when using the 10.5 or 10.6 SDK

(cherry picked from commit 2619d2f6a9d2fb47712a01066b7d49aefd6b874b)

modules/gui/macosx/CompatibilityFixes.h

@@ -79,8 +79,6 @@ extern OSErr UpdateSystemActivity(UInt8 activity);
 #pragma Fixes for OS X Snow Leopard (10.6)
 
 #ifndef MAC_OS_X_VERSION_10_7
-extern NSString *const NSAccessibilityFullScreenButtonAttribute;
-
 enum {
     NSWindowCollectionBehaviorFullScreenPrimary = 1 << 7,
     NSWindowCollectionBehaviorFullScreenAuxiliary = 1 << 8

modules/gui/macosx/MainWindowTitle.m

@@ -421,9 +421,12 @@
 
 @end
 
+
 @implementation VLCCustomWindowFullscreenButton
+#ifdef MAC_OS_X_VERSION_10_7
 - (id)extendedAccessibilityAttributeValue: (NSString*)theAttributeName {
     return ([theAttributeName isEqualToString: NSAccessibilitySubroleAttribute] ? NSAccessibilityFullScreenButtonAttribute : nil);
 }
+#endif
 
 @end