Using X properties for the openmoko-footer

[Rob Bradford]

I've posted an explanation and reference code to Bugzilla #43.

Here is a short recap, however i'd prefer it if the conversation
remained on that bug in order to keep it all together.

Since the purpose of the footer (as far as I can make out from the wiki)
is to only show information from the client with the topmost window I
would suggest tracking the X _NET_WINDOW_ACTIVE property and then using
a moko specific property to provide this information rather than using
dbus to update the footer.

I think that this approach should give better performance with lower
latency, it should also require fewer context switches which are painful
on ARM. Another benefit of this approach is that all applications will
not need to link with dbus and the overhead that that brings.

Cheers,

Rob