Save moving the "new" row

Previously, we actually moved one more line back than we had to.
This only moves lines back that need to remain where they were.

This shaves another couple seconds off the benchmark.

src/conio/bitmap_con.c

@@ -1400,13 +1400,12 @@ bitmap_movetext_screen(int x, int y, int tox, int toy, int direction, int height
 			direction = 1;
 		else
 			direction = -1;
-		height = vstat.rows - height;
+		height = vstat.rows - (height + (y - toy));
 		// If everything was moved, there's no lines to move back
-		if (height <= y - toy)
+		if (height <= 0)
 			return;
-		int otoy = toy;
-		toy = vstat.rows - (y - toy);
-		y = toy - (y - otoy);
+		toy = vstat.rows - (height - 1);
+		y = toy - (height);
 	}
 
 	int maxpos = screena.screenwidth * screena.screenheight;