Don't use __glibcxx_assert to check class invariants

Don't use __glibcxx_assert to check class invariants

Assertions should be used to check preconditions that users must meet,
not to check whether the implementation is correct.

	* include/bits/regex_automaton.tcc (_StateSeq<_TraitsT>::_M_clone()):
	Remove __glibcxx_assert statements and use map::find instead of
	map::operator[].

From-SVN: r264422