From Stephan Huber, "minor ios-fixes/-enhancements

* force _OPENTHREADS_ATOMIC_USE_BSD_ATOMIC for IOS device + simulator as the test does not pick the right implementation
* fixed a small compile-bug for iphone-example
* added a check to prevent multiple realization of a GraphicsWindowIOS-object
"

src/osgViewer/GraphicsWindowIOS.mm

@@ -746,6 +746,8 @@ void GraphicsWindowIOS::init()
 
 bool GraphicsWindowIOS::realizeImplementation()
 {
+    if (_realized) return true;
+    
     NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
     
     BOOL bar_hidden = (_traits->windowDecoration) ? NO: YES;