Log a stack trace for obscenely huge dirty regions.

If we're freaked out enough that we're carping & ignoring it, I want to
be able to actually figure out what's broken.

git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@906 ed5b42cb-e716-0410-a449-f6a68f950b19

src/java/com/threerings/media/RegionManager.java

@@ -78,7 +78,7 @@ public class RegionManager
         // more sanity checking
         long x = rect.x, y = rect.y;
         if ((Math.abs(x) > Integer.MAX_VALUE/2) || (Math.abs(y) > Integer.MAX_VALUE/2)) {
-            log.warning("Requested to dirty questionable region", "rect", rect);
+            log.warning("Requested to dirty questionable region", "rect", rect, new Exception());
             return; // Let's not do it!
         }