climbing back to the Castle (trunk only)

climbing back to the Castle (trunk only)

     From the newsgroup:  someone using <Someone>'s level-flip patch
(to transpose special levels left-to-right or top-to-bottom or both in
order to get more variety from them) ended up in solid rock.  When
climbing the stairs up from the Valley to the Castle, goto_level() was
hardcoded to find a spot in the extreme lower right corner.  If the level
is turned upside down, solid rock from an unused row at the top edge of
the map ends up at the bottom, and the placement code could put the hero
there.  That code only checked for walls and monsters being in the way,
not rock.  Also, if the level is flipped side-to-side than hero ends up
in same area as the upstairs rather than on opposite side of the Castle.

     This switches to the same teleport-region code used for other level
changes which don't arrive on stairs; such regions get flipped along with
map by that patch (I hope).  Even though no such fix is currently needed
for unmodified nethack, this change gets rid of the special case Castle
placement code entirely, simplifying both goto_level() and u_on_sstairs()
in the process.

     The Castle's existing from-below region covers the rightmost half-
dozen or so columns across all rows, so offers a bigger landing zone than
just the bottom corner.  That could be tweaked within castle.des but I
don't think it needs to be.