CppRewriter: Treat libc++'s std::__1:: as std:: for debugger display

Change-Id: Iabc1330633e5568b7c94059d4286c93adfecb1a2
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>