cocoa: Avoid deprecated NSOpenPanel filename method

Avoid the NSOpenPanel filename method (deprecated in MacOSX 10.6)
in favour of using the URL method and extracting the path from the
resulting NSUrl object.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAndreas Färber <andreas.faerber@web.de>

ui/cocoa.m

@@ -810,7 +810,7 @@ QemuCocoaView *cocoaView;
         exit(0);
     } else if(returnCode == NSOKButton) {
         const char *bin = "qemu";
-        char *img = (char*)[ [ sheet filename ] cStringUsingEncoding:NSASCIIStringEncoding];
+        char *img = (char*)[ [ [ sheet URL ] path ] cStringUsingEncoding:NSASCIIStringEncoding];
 
         char **argv = (char**)malloc( sizeof(char*)*3 );