Objective-C usage can result in undefined behavior (part 2)

Hi vestbo,

do you remember the Apple category problem with QtExtras? If this and all other categories are not packed in a namespace, it will result in a crash if many plugins running Qt with different Qt versions. We discussed that problem last year.

You can read more here : QTBUG-100059

Now, a new category raised in Qt called "QtSandboxHelpers". 
File : src/corelib/kernel/qcore_mac_p.h

To fix it the same strategy can be used again 

Old 
// @compatibility_alias doesn't work with categories or their methods
#define QtExtras QT_MANGLE_NAMESPACE(QtExtras)

New 
// @compatibility_alias doesn't work with categories or their methods
#define QtExtras QT_MANGLE_NAMESPACE(QtExtras)
#define QtSandboxHelpers QT_MANGLE_NAMESPACE(QtSandboxHelpers)

Thank you,
Michael.