fix issue #1025 - stuck in Mines' End

Issue reported by AndrioCelos:  if you arrived at the Wine Cellar
variation of Mines' End by falling or by level teleportion instead
of via the stairs, you could end up in the treasure chamber.  If
you lacked a way to dig or to level teleport, you would be stuck.
Since most of that level is undiggable, it would likely fill up with
monsters before one that could dig would appear close enough to dig
to you and you'd eventually starve.

The initial report suggested including an escape item in the treasure
chamber.  This adds a teleport region to control hero's arrival spot
instead.  There was a suggestion fix things this way from copperwater
but I didn't notice that until I had already chosen this method....

Fixes #1025

dat/minend-2.lua

@@ -55,6 +55,11 @@ if percent(50) then
    end
 end
 
+-- uncontroled arrival (via trap door, level teleport) will be in the central
+-- portion of level to prevent ending up stuck in the treasure area, whether
+-- arriving from above or below (despite this being bottom of Mines branch,
+-- hero might arrive from below by invoking Wiz role's Eye of the Aethiopica)
+des.teleport_region({ region={23,03,48,16}, region_islev=1 })
 
 -- Dungeon Description
 des.feature("fountain", {14,13})