vout_macosx: check whether the receiving window can respond to non-standard calls prior to calling them (close #6034)

If the interface script has nothing to do, then it can simply end and
the let the interface thread finish ahead of pf_deactivate.
This will _not_ automatically cause VLC to exit.

If there is nothing to do, then the interface thread can finish.

The Lua interpreter is not thread-safe. So this API made absolutely no
sense: the timer callback is called asynchronously from another thread.
Fortunately, none of our Lua scripts used this except for testing.

(This should probably be moved to Lua code.)

Pointed-out-by: Edward Wang <edward.c.wang@compdigitec.com>

The function is a bit ugly but it's difficult to do this using
pure arithmetic.

Fixes #6378

Till now, when a tooltip showed up, the underlying main window lost
keyboard focus (keys + mouse wheel). Users had to click again on the window
to regain this focus.

this patch mainly uses a flag that enables to display a window without
activating it (see msdn doc) plus a bit of cosmetics.

this patch should be backported.

Note that all current configcontrol are instanciated using the
existing gridlayout constructor by createConfigControl().
We probably can drop constructors for self contained configcontrols.

They would not work with IDirect3DDevice9::StretchRect
See:
http://forum.videolan.org/viewtopic.php?f=14&t=99498
http://forum.videolan.org/viewtopic.php?f=14&t=99235
http://forum.videolan.org/viewtopic.php?f=14&t=98882
http://forum.videolan.org/viewtopic.php?f=14&t=98514

This is necessary to track the issues we have on XP with some GPU.

end of the stream. This is wrong and the patch fix that.
Signed-off-by: Hugo Beauzée-Luyssen <beauze.h@gmail.com>