Debugger: Make dumper work with GDB 7.7

GDB 7.7 changed behavior e.g. for the names of anonymous fields,
we need to adjust dumpers and some tests.

Change-Id: I25ae32cc56c4ff63b677a04d6ed9c250e0252140
Reviewed-by: Eike Ziller <eike.ziller@digia.com>