Raspistill: Correct help text for DateTime (year not included)
Raspistill: Correct help text for DateTime (year not included)

Year is not included in the filename as the 32 bit integer would
overflow. Not updating to a 64bit int as the string format is
passed in from the client, so would break compatibility.

https://github.com/raspberrypi/userland/issues/274

kraj/userland,ethanol100/userland,6by9/userland,luked99/userland-1,6by9/userland,JamesH65/userland,gonzoua/userland,luked99/userland-1,JamesH65/userland,adamheinrich/userland,roberttidey/userland,kraj/userland,luked99/userland-1,raspberrypi/userland,raspberrypi/userland,adamheinrich/userland,roberttidey/userland,maroviher/userland,maroviher/userland,6by9/userland,roberttidey/userland,adamheinrich/userland,kraj/userland,raspberrypi/userland,ethanol100/userland,maroviher/userland,gonzoua/userland,JamesH65/userland,gonzoua/userland,ethanol100/userland