Some applications need to access gdk_quartz_window_get_nsview,
gdk_quartz_window_get_nswindow, and gdk_quartz_event_get_nsevent
so move these from the private gdkquartz-gtk-only.h to a new
header gdkquartz-cocoa-access.h. Don't include this header in
gdkquartz.h so that user code that doesn't need to access these
functins isn't required to compile with Objective C/C++.
Closes https://gitlab.gnome.org/GNOME/gtk/-/issues/1737
gtk+-3.24.14 with quartz backend fails to compile on macOS when using
a case-sensitive file system. The cause for the compilation error is a
simple typo in line 26 of `gdk/quartz/gdkquartz-gtk-only.h`. The
AppKit framework is included there with `<Appkit/Appkit.h>` instead of
`<AppKit/AppKit.h>`, which is fixed with this commit.
References: https://trac.macports.org/ticket/60168
Fixes: https://gitlab.gnome.org/GNOME/gtk/issues/2503
Closes: https://gitlab.gnome.org/GNOME/gtk/issues/1737
Don't export any functions taking or returning MacOS types in
gdkquartz.h, gdkprivate-quartz.h, or any header that either includes.
The GdkQuartz internal functions are moved to a new header
gdkinternal-quartz.h, the functions used by quartz-specific
Gtk files are moved to another new header gdkquartz-gtk-only.h, and
the key and event enums to a new header gdkkeys-quartz.h.
