Added TimeOfDay hooks

Added TimeOfDayHour hook, called every hour change, with the argument of
the new hour (0 - 23).
Added TimeOfDayMinute hook, called every minute change, with the
argument of the new hour (0-23) and minute (0-59)

Added a callback for the weather_daylength convar, to prevent the
noticable delay when you change to a lower day length