Fix up Debugger helpers to be able to dump QObject's with CDB.

- Make container dumper routines set "childnumchild" when known
  in order to avoid roundtrips; avoid repeated invocations of
  container.end().
- Completed dumper information in some places to avoid roundtrips.
- Extended QVariant helpers by dumpers for common GUI types
  (rectangles, points, sizes, fonts, size policies).
- Introduced artificial QObjectChildList/QObjectProperty types to
  be able to dump QObject children and properties without using
  gdb expressions.
- Fixed dumping of Signal/Slot list to pass on correct types. Avoid
  recursions if signal is connected to self.
- Replaced expressions by addresses in the dumpers to it make work
  for CDB.
- Reworked dumper test program to have -a, making it usable for tests,
  add further types.
- Gdb: Clear output buffer before calling dumpers, avoiding mixups
  in case evaluation of expression fails.
- Fix the dumper parser used by CDB, do not be fooled by
  "<synthetic>" addresses, etc.
- Pass on a "dumperVersion" in initial query.