Eventually indexed property query callbacks will return attributes
(as an integer) or an empty handle if property is not intercepted.

To gradually migrate to this new API, USE_NEW_QUERY_CALLBACK
macro would control if old or new style API is used.

So the migration plan is:

1) introduce new API which should be explictily enabled;
2) switch to new API defining USE_NEW_QUERY_CALLBACK before
include of <v8.h> (that would require changes to client code as well)
3) remove old API from v8
4) remove #define USE_NEW_QUERY_CALLBACK from clients.

BUG=http://code.google.com/p/v8/issues/detail?id=816

Review URL: http://codereview.chromium.org/3101001

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5228 ce2b1a6d-e550-0410-aec6-3dcde31c8c00