some lint cleanup

Building with an old version of gcc with various warnings enabled
generated a lot of noise.  Most of it was due to not guarding string
literals with `const', but there were a couple of actual problems too.

src/polyself.c

@@ -619,7 +619,7 @@ break_armor()
 
 		/* Future possiblities: This could damage/destroy helmet */
 		Sprintf(hornbuf, "horn%s", plur(num_horns(youmonst.data)));
-		Your("%s %s through %s %s.", vtense(hornbuf, "pierce"),
+		Your("%s through %s %s.", vtense(hornbuf, "pierce"),
 		     shk_your(yourbuf, otmp), xname(otmp));
 	    } else {
 		if (donning(otmp)) cancel_don();