Unordered container local_iterator range shall not contain any singular
iterator unless both iterators are both value-initialized.
libstdc++-v3/ChangeLog:
* include/debug/safe_local_iterator.tcc
(_Safe_local_iterator::_M_valid_range): Add _M_value_initialized and
_M_singular checks.
* testsuite/23_containers/unordered_set/debug/114316.cc: New test case.