re PR libstdc++/69450 (libstdc++-v3/include/math.h:66:1 2: error: 'constexpr bool std::isnan(double)' conflicts with a previous declaration)

	PR libstdc++/69450
	* acinclude.m4 (GLIBCXX_CHECK_MATH11_PROTO): Split check for obsolete
	isinf and isnan functions into two independent checks.  Check on hpux.
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* include/c_global/cmath (isinf(double), isnan(double)): Use
	_GLIBCXX_HAVE_OBSOLETE_ISINF and _GLIBCXX_HAVE_OBSOLETE_ISNAN,
	respectively.

From-SVN: r232925