C++ testsuite changes

[Michael Elizabeth Chastain]

> I would really prefer it if you didn't rewrite the tests to accomodate
> the ABI change (a very specific change) and change all sorts of other
> tests at the same time.  It makes it impossible to tell from your
> patches when you make a change like this one.

Sigh, you're right.  I should have done this in several stages,
where the first stage is lot of gdb_test_multiple with no change
in output.

I can go back and make it that way if you want.  Shall I do that?

> Eh... why don't you?  It's a feature that we don't print the virtual
> base pointer in recent gcc/dwarf combinations.

Of course it's acceptable if gdb does *not* print the virtual base
pointer.

If gdb *does* print a virtual base pointer, do we consider that a
bug in gcc?  Because that's what "XFAIL" means.  Or is it a bug in gdb?
Then I should file a PR for it.

My opinion is that we should just accept it.  There's far worse bugs
in C++ support that aren't getting any attention.

Michael C