Removed several more different 'iterators.h' files in libcxx/test

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@171452 91177308-0d34-0410-b5e6-96231b3b80d8
Removed another copy of  'iterators.h' files in libcxx/test

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@171456 91177308-0d34-0410-b5e6-96231b3b80d8
...and then there was one. Only one copy of 'iterators.h' in the test tree for libc++

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@171479 91177308-0d34-0410-b5e6-96231b3b80d8
atomic_bool was missing (just a typedef to atomic<bool>).

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@171498 91177308-0d34-0410-b5e6-96231b3b80d8