Instead of using Xlib for parsing resource files, this now uses the
dedicated xcb-based library that is meant for exactly this task.
Fixes: https://github.com/awesomeWM/awesome/issues/1176
Signed-off-by: Uli Schlachter <psychon@znc.in>
The documentation states that this function returns nil if the property does not
exist, but it actually returned nothing. And yes, in Lua this is a difference...