Start off newly generated worlds early at sunrise, 5:15am (#6211)

Start off newly generated worlds early at sunrise, 5:15am (#6211)

Gives starting singleplayer games this subtle "dawn of a new world" feel.
I would have set it even earlier (up to 4:45am), but I was worried that in
some pre-existing games the player could be overwhelmed by hostile
mobs right at the start, seriously changing gameplay.

It's just the default, individual games should be able to override it, and
for public servers it's irrelevant anyway, because only the first player to
set foot in the world will notice, and that's usually the server admin.