Revert 240682 "Add libc++ and libc++abi to third-party."

This change broke deps2git.  We will add the repos in a bit and
we'll add check_deps2git to the CQ.

> Add libc++ and libc++abi to third-party.
> 
> BUG=318770, 313751
> R=glider@chromium.org,thakis@chromium.org,bradnelson@chromium.org,darin@chromium.org
> 
> Review URL: https://codereview.chromium.org/75213003

TBR=alextaran@chromium.org

Review URL: https://codereview.chromium.org/110333004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240706 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240706