[V8] Add a "fallback" mode for named property interceptors

[V8] Add a "fallback" mode for named property interceptors

By default interceptors are called before the normal property
resolution on objects.  When an interceptor is installed as a
"fallback" interceptor, it is only called if the object doesn't
already have the property.

In the case of a global object having an fallback interceptor,
the interceptor is not invoked at all for var or function
declarations.

Change-Id: Ia8c2b4d37070c97d9ef327da9e62d431427afe89
Reviewed-by: Kent Hansen <kent.hansen@nokia.com>