FOR_NSCREENS() is just alias for FOR_NSCREENS_BACKWARD(). In many cases
it really matters that we're going backwards and the last iteration visited
the screen #0, and that one is panoramix-wrapped.
Thus directly calling FOR_NSCREENS_BACKWARD() here and dropping the alias.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>