Also run excluded examples when turning run_all_when_everything_filtered on.

Created by: janv

I'm not sure if this was an intentional omission, but when an exclusion filter removes exampels from a run, the run_all_when_everything_filtered option does not bring them back, even if, for example, you have an entire file marked as :slow => true and try to run just that file.

The changes I made in this request are not yet ready to be merged!

I'm not quite sure what's going on in the second half of the World#announce_filters method and also my change breaks a few examples from the example_group_spec.

I'd like to get some feedback on this and maybe get an explanation for the current behavior or some help in developing the solution into something that works and doesn't break other stuff.