Add fixits for messaging self in MRR or using super, as the intent is
clear, and it turns out people do that a lot more than expected.
Allow for objc_direct_members on main interfaces, it's extremely useful
for internal only classes, and proves to be quite annoying for adoption.
Add some better warnings around properties direct/non-direct clashes (it
was done for methods but properties were a miss).
Add some errors when direct properties are marked @dynamic.
Radar-Id: rdar://problem/58355212
This diagnostics reads a bit awkward when a property is conflicting with a property, since the the first half of the diagnostic is talking about the property declaration, but the second half is implicitly referring to the generated getter/setter.