Changes

[libc++] Support no libc++ namespace in the iterator test.

The 5f12f4ff9078455cad9d4806da01f570553a5bf9 commit suppress printing of
inline namespace names in diagnostics by default that breaks the libc++
iterator test, which expects __1 in the namespace.

This patch fixes the test by supporting a test case without __1 in the
namespace.

Differential Revision: https://reviews.llvm.org/D92142