There's a clang bug [2] where if a selector is marked as unavailable,
it's marked as unavailable for every class, not just the class where
the unavailable selector is.
This means that we can't do `[super initWithCoder:x]` anywhere,
because `initWithCoder:` is marked as unavailable for UIActivityViewController.
So instead rewrite the call to super to call objc_msgSendSuper
directly, circumventing clang's broken availability checks.
[1] https://bugzilla.xamarin.com/show_bug.cgi?id=41319
[2] https://llvm.org/bugs/show_bug.cgi?id=28058
Support binding NSObjects as IntPtr. This is usually not
a problem, because when we fetch the ObjC signature for a
method, we usually get the signature as exported by us,
(in which case a parameter bound as 'IntPtr' would be treated
as 'void *' in the dynamic registrar) *except* when the
selector corresponds with a protocol the type implements,
in which case we get the signature as defined in the protocol.
https://bugzilla.xamarin.com/show_bug.cgi?id=41132
Rolf Bjarne Kvinge