If we have an input parameter (or return value) we need to use (nullable).
However, if it is an (inout) or (out) parameter, (optional) is sufficient.
It looks like (nullable) could be used for everything according to the
Annotation documentation, but (optional) is more specific.
* Only check __OBJECT_ATTRIBUTES_DEFINED and __UNICODE_STRING_DEFINED
on MinGW (MSVC doesn't have these)
* MSVC: disable:4005 when including windows.h and ntstatus.h
* Move NTAPI cconv into the parens with the NtQueryKeyFunc
* Fix return values in some functions
https://bugzilla.gnome.org/show_bug.cgi?id=734888
