[libstdc++] remove __compare_and_swap

[Gabriel Dos Reis]

Benjamin Kosnik <bkoz@redhat.com> writes:

| Phil, I am in support of your planned removal of these functions. So is 
| Mark. If you get the approval of Gaby or Loren (with Loren being the maintainer 
| most important in this discussion, obviously) I think you can proceed. I 
| think this is a fair way to resolve this.

Hi Benjamin,

I agree with Nathan's long term vision about the issue. However, I also 
agree with Phil that we can just remove it and add it back if really
needed -- at that time we'll provide a solid documentation, showing
what it is there for.  Otherwise, it gets port maintainers confused.

-- Gaby