The nit_focus component implements the input-focus policy for the nitpicker
GUI server. It consumes nitpicker's 'clicked' report and, in turn, produces a
'focus' report to be consumed by nitpicker.

Focus changes are subjected to a configurable policy, which is selected via
Genode's regular policy-selection mechanism based on the label of the clicked
nitpicker client. The client is focused only if the policy has the attribute
'focus' set to "yes".
