PR libstdc++/53270
	* include/ext/concurrence.h (__mutex, __recursive_mutex, __cond): Use
	NSDMI in C++98 mode too.
	* include/ext/rope: Add system_header pragma.
	(_Refcount_Base, _Rope_RopeRep): Use NSDMI.
	(_Rope_RopeRep::~_Rope_RopeRep): Destroy mutex.

From-SVN: r189553