Remove assorted dead code.

Assignments that are overwritten shortly afterwards and never used,
and a completely unused variable. Also, the bogus array access in
testbn.c could have actually accessed one beyond the array limit
(though of course it's only in a test harness).

sshzlib.c

@@ -267,7 +267,6 @@ static void lz77_compress(struct LZ77Context *ctx,
 	    }
 	} else {
 	    nmatch = 0;
-	    hash = INVALID;
 	}
 
 	if (nmatch > 0) {