osx 64 bit multilib build needs an explicit export as in this architecture our visibility flags get respected for obj-c classes as well

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67575 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/cocoa/private.h

@@ -352,7 +352,7 @@ protected :
     - (void)sheetDidEnd:(NSWindow *)sheet returnCode:(int)returnCode contextInfo:(void *)contextInfo;
     @end
 
-    @interface wxNSAppController : NSObject wxOSX_10_6_AND_LATER(<NSApplicationDelegate>)
+    WXEXPORT @interface wxNSAppController : NSObject wxOSX_10_6_AND_LATER(<NSApplicationDelegate>)
     {
     }