PR libstdc++/69626
	* acinclude.m4 (GLIBCXX_ENABLE_C99): Check C99 stdlib.h functions
	with -std=c++98 and define _GLIBCXX98_USE_C99_STDLIB.
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* testsuite/21_strings/c_strings/char/69626.cc: New.

From-SVN: r233161