Set the stopped flag for the debugger proxy when it receives a quit command, so that the proxy exits a bit quicker and cleaner. Add a timeout to the cleanup quite of test_debugger, so that it does not hang when a test goes wrong. Add some more tracing.
This change is mostly for FB internal organizational reasons.
Building is not effected beyond the fact that the target now
lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.