debugger: add semi-automated test for display of anon structs.

http://sourceware.org/bugzilla/show_bug.cgi?id=10586. fsf gdb errors out
on -var-list-children on an anonymous union. The proposed fix has been
reported to crash gdb steered from eclipse.
(http://sourceware.org/ml/gdb-patches/2011-12/msg00420.html

).
We should not be affected as mac gdb was fixed in 2006 and we avoid
using varobjs when we have python.

Change-Id: I2698d6762ed8757549bad304c6cd23d9150460fd
Reviewed-by: hjk <qthjk@ovi.com>