CDB: Bug fixing

- Turn off initial breakpoint when attaching (terminal) and
  additionally ignore it before the first startup complete
- Refuse to step  the artifical thread created when
  interrupting
- If possible, switch to thread 0 when interupting (do not
  use artificial thread)
- Ignore non-fatal exceptions in dumper calls (stray Startup-
  complete-traps)
- Use right thread for dumper call loading
- Rename windows exception code enumeration
- Turn off modification off watch-data children by setType,
  show empty lists correctly.
- Verbose warnings about inserting invalid watch data.