Pass last receieved event timestamp when required
The EWMH specifications require that the timestamp of the last
user interaction should be sent to NET_ACTIVE_WINDOW.
Since GLFW send just 0 currently, the GNOME Shell would issue a warning
upon receiving a NET_ACTIVE_WINDOW message:
Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0
This commit fixes this by sending lastKeyTime as the timestamp
which should be a reasonable approximation to the last user interaction.
I have not tested this patch extensively, but it silences the warning and it should not alter existent behaviour.
For further information about NET_ACTIVE_WINDOW/EWMH, consider the online reference
I started on a full implementation of this requirement a while back in the x11-event-time branch. Note that it is not complete.