replMain doesn't exit when windows are closed

[ericu]

Sorry, one more replMain issue. When you're using it and you close the last window, the program's still running and you have to ctrl-c out to get back to the repl. If you run main instead, exiting the last window exits the program all the way back to the repl. It's a minor nit, but I just noticed it. I can reproduce this in hello-world in 0.8.0.2. Apologies if this is known/accepted behavior.