Debugger: Rework GDB disassembly display

- Use exclusively CLI to retrieve information. MI output misses parts.
- Remove MI output handling
- Re-order lines in ascending address order in mixed output.
  GDB orders by source line, but that's confusing when stepping
- Introduce a new 'hunk' field for source lines to give a hint
  which part of a split source line we are looking at.

Change-Id: I61a547503e9a18f95e99b897e26dbb207cabb8cf
Reviewed-by: David Schulz <david.schulz@digia.com>
Remove dead code.

Change-Id: I041638c5237ee2752c5bc0fb9e1c8e73f15b247e
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>