The position window is currently just a debug helper, that can only be
enabled by explicitly passing extra CFLAGS (-DSHOW_POSITION).

Some distros already do that, but that's rather invasive from distro pov
(using such undocumented tricks isn't actually a clean approach), and
users asked for this as a general feature.

A trivial solution is adding a configure option for that. It still needs
to be enabled at compile-time, but at least needs less special hacks
and easier to maintain by standard distro build machineries.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>