lit and unlit corridors

lit and unlit corridors
The default symbol for lit and unlit corridors are the same.  This makes
the lit_corridor option a no-op where the defaults are used and also means
that using a light scroll/spell a corridor has no obvious effect.  To
address that, I special-cased the lit corridor symbol and change its color
to bright white when its the same symbol as the unlit corridor symbol (I
didn't change the default color since I thought that made the lit corridor
look strange using the windows console interface).