Reported by AndrioCelos, a handful of objects in the tutorial can
be discovered via use, and such discoveries were carrying over to
normal play when the tutorial ended.
This causes the hero to forget such discoveries. The player will
still be able to remember them. The proper fix would be to discard
the initialized but not-yet-started game when entering the tutorial
and then start a whole new one when exiting so that saving and
restoring game state would become unnecessary. This doesn't do that.
This also causes monster birth and death statistics to be reset when
exiting the tutorial. Affects the #vanquished command and potentially
extinctionist play.
Closes#1134
a79d6d8e63