Fixes#217
Feedback when spellcasting monster aimed at the wrong spot due to not
being able to see an invisible hero only gave the intended message if
hero couldn't see self. The code was using 'if (Invisible)' which
checks whether the hero is invisible and can't see invisible, when it
should have been using 'if (Invis)' which just tests whether the hero
is invisible.
It wouldn't surprise if the same problem occurs elsewhere. Those
macros are rather error prone.
The issue report mentions that one of the affected messages might be
unreachable. I didn't investigate that.
8cf70f7771