PR libstdc++/78968
	* config.h.in: Regenerate.
	* configure: Likewise.
	* configure.ac: Check for __cxa_thread_atexit.
	* libsupc++/atexit_thread.cc [_GLIBCXX_HAVE___CXA_THREAD_ATEXIT]:
	Don't define __cxa_thread_atexit if libc provides it.

From-SVN: r244057