when encountering a hiding monster that's still unseen after being
revealed (so most likely invisible when hero lacks see invisible).
Change
|Wait! There's an it hiding under <an object>!
to
!Wait! There's something hiding under <an object>!
when hero tries to move onto the object.
Also, when a hidden monster reveals itself by attacking, change
|It was hidden under <an object>!
usually followed by "It hits." or "It misses."
to
|Something was hidden under <an object>!
without changing whatever follows.
Fixes#542
ee13fb36ac