Only blink the info LED if the user hasn't pressed a button for 30 seconds.

Created originally on Bitbucket by chrisball (Chris Ball)

Was already merged in Bitbucket before import, marked as merged by the import user

Having the info LED blink while composing a shot in the viewfinder is very distracting to me, because I use my right eye on the viewfinder -- this way, doing something like pressing a half-shutter or the Play button will postpone the next blink until thirty seconds after inactivity.

Tested on 5d2, seems to work as expected.