Can't bind annotated Injector

_From [zorzella](https://code.google.com/u/117480957020302471907/) on September 30, 2009 12:29:24_

In GuiceBerry, it's common for tests to want to access the server's injector. For
that, I want to be able to do something like:

bind(Injector.class).annotatedWith(ServerSide.class).toInstance(serverInjector);

Unfortunately, Guice currently arbitrarily forbids binding an Injector, even if
annotated.

_Original issue: http://code.google.com/p/google-guice/issues/detail?id=433_