This is intended to address a couple quirks with force-fighting an
unoccupied spot that I noticed:
* Now that furniture is considered 'solid', an object is much more
likely to be sitting on the square, obscuring the terrain glyph. As
a result, the current glyph is no longer sufficient to accurately
describe the contents of the spot -- e.g., an altar with a corpse on
top of it was being described as "an unknown obstacle", even when the
hero knew exactly what furniture was there.
* When blind and attacking an unexplored 'solid' square, the attacked
position would always be described as 'the stone', even something
like a fountain or sink which didn't seem likely to be confused with
a stone wall.
* The feedback for attacking stone was previously changed from 'solid
rock' to 'stone' in order to be consistent with the feedback for
attacking an unseen wall, but they still weren't quite the same
("stone" vs "the stone").
* The 'stone' feedback for all STONE/SCORR spots was incorrect on
levels flagged as arboreal, where stone is rendered and described as
trees.
This relies on back_to_glyph for positions where the hero is aware of
the terrain and certain other spots (like stone, walls, etc) for which
back_to_glyph produces good results even if they're unseen, and falls
back to the generic "unknown terrain" in other cases.
Pretty long commit message for such a small commit, but oh well...
d3d5f7f88b