Focus history: Don't ignore unfocusable clients

The only caller of focus.history.add() should be the "focus" signal, so at that
time the unfocusable client already does have the focus. At that point, there is
no reason why this shouldn't be recorded in the focus history.

(And yes, unfocusable clients can be focused. Don't ask.)

This should hopefully fix FS#778.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/awful/client.lua.in

@@ -131,13 +131,11 @@ end
 --- Update client focus history.
 -- @param c The client that has been focused.
 function focus.history.add(c)
-    if focus.filter(c) then
     -- Remove the client if its in stack
     focus.history.delete(c)
     -- Record the client has latest focused
     table.insert(data.focus, 1, c)
 end
-end
 
 --- Get the latest focused client for a screen in history.
 -- @param screen The screen number to look for.