Bring the baby back: longpress back button to kill the app [1/2]

this old CM baby (made by @rascarlo) is still useful till
kufi does his magic on the navbar :D

Change-Id: Ic8a94679226cc5f575bd670251db978797af96d0
Merge remote-tracking branch 'slimroms/lp5.0' into lp5.0