While running the tutorial, the Save command is disabled. When the
tutorial was extended to two levels, stashing and restoring the
hero's equipment stopped working as intended if player entered the
second level. The attempted fix for that broke re-enabling Save
even if the player left the tutorial without entering its second
level.
This seems to fix things, but I'm flailing around with barely a clue
here. A couple of simpler attempts didn't work and I haven't figured
out why, so this is a bit more complex than what I wanted.
Reorganizing nhl_callback() isn't part of the fix, just avoids use
of some redundant code.
Reported by Noisytoot: going from level tut-1 to tut-2 returned the
hero's starting equipment too soon, and exiting the tutorial from
tut-2 let the hero keep any equipment acquired within the tutorial.
Entering and leaving the tutorial was being handled by lua code in
the level description of tut-1 and adding a second level messed that
up. I didn't see any way of handing that with level-specific lua
code so I made it become the core's responsibility. gotolevel()
knows when the hero is moving from one dungeon branch to another so
it can recognize entry to or exit from the tutorial easily.
While fixing this, prevent #invoke of the Eye of the Aethiopica from
offering the tutorial as a candidate destination (was feasible if it
had been entered at start of game).
Not fixed: levels visited in the tutorial become part of #overview.
Show location as "Tutorial:1" instead of "Dlvl:1" on status lines.
Only tested with tty; some interfaces handle location themselves and
may need their own fixup for this.
Fixes#1046
