Fixed: Compilation with OS X SDK 10.10

--HG--
branch : develop

code/nel/src/3d/driver/opengl/driver_opengl_window.cpp

@@ -1483,7 +1483,7 @@ bool CDriverGL::createWindow(const GfxMode &mode)
 		[[CocoaApplicationDelegate alloc] initWithDriver:this];
 
 	// set the application delegate, this will handle window/app close events
-	[NSApp setDelegate:appDelegate];
+	[NSApp setDelegate:(id<NSFileManagerDelegate>)appDelegate];
 
 	// bind the close button of the window to applicationShouldTerminate
 	id closeButton = [cocoa_window standardWindowButton:NSWindowCloseButton];