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Hi, Libc++ has been shipping the <ext/hash_set>, <ext/hash_map> and <ext/__hash> headers for a while and they are deprecated. Those headers contain data structures like __gnu_cxx::hash_map that have replacements like std::unordered_map. I would like to remove those headers. I've put up a patch for review but I won't commit it until we have a sort of plan because I know