Don't delete event handlers in messages on layout/resize

When `layout` was called, it rebuilt the messages area from scratch
using its html.  This resets any event handlers on nodes embedded in
these, so a layout would strip out event handlers from the input box,
including the ones that return the game to its normal state once you're
done with the box.  The result was that you had to reload the browser to
get something playable.  This was triggered by any resize, which in
several browsers (and possibly sensitive to other settings, such as
zoom) can result from a browser find command (10318), especially since
crawl doesn't swallow ctrl-f when the search box was open. A re-layout
is also apparently triggered when a spectator joins (10938).

This fix, instead of rebuilding the messages panel from html, makes a
deep copy of it using jquery `clone`, in a way that preserves event
handlers.  Layout still copies other areas using html, so if anyone ever
adds any event handlers in the stats area, this could come up again.
Supposedly, the html way is faster, so I left this as-is.

(I'm not entirely sure why this would be the best way to do what
`layout` is doing in the first place, but I'll leave that for more
skilled javascript people.)

crawl-ref/source/webserver/game_data/static/game.js

@@ -54,14 +54,17 @@ function ($, comm, client, dungeon_renderer, display, minimap, enums, messages,
         $("#stats").html(old_html);
 
         // Determine height of messages area
-        old_html = $("#messages").html();
+
+        // need to clone this, not copy html, since there can be event handlers
+        // embedded in here on an input box.
+        var old_messages = $("#messages").clone(true);
         var old_scroll_top = $("#messages_container").scrollTop();
         s = "";
         for (var i = 0; i < msg_height+1; i++)
             s = s + "<br>";
         $("#messages").html(s);
         var msg_height_px = $("#messages").outerHeight();
-        $("#messages").html(old_html);
+        $("#messages").replaceWith(old_messages);
         $("#messages_container").scrollTop(old_scroll_top);
 
         var remaining_width = window_width - stat_width_px;