Autologin timeout countdown should stop on user input

[pezcurrel]

When autologin is active the "countdown" should stop on user input in order for the user to have the time to select a different user and type the password even when autologin-user-timeout is set to low values (eg 5 seconds or so). Unity greeter cancels the timer when switching users. liblightdm-gobject provides a lightdm_greeter_cancel_autologin method for this.

[pezcurrel (pezcurrel)]

I propose these 2 patches mostly as a "proof of concept". They enable the user to cancel autologin by just clicking on the background. Surely it could be done much better, with, say, a button somewhere stating "Cancel autologin", but I'm not a coder. Anyway I do propose these patches to hopefully get some attention on this issue which makes lightdm-gtk-greeter mostly unusable in one of its main purposes (switching user) when autologin timeout is set to low values, like 5 seconds or so.