* configure.ac: Check for C11 timespec_get function.
	* crossconfig.m4 (freebsd, linux, gnu, cygwin, solaris, netbsd)
	(openbsd): Likewise
	* config.h.in: Regenerate.
	* configure: Regenerate.
	* include/c_global/ctime (timespec, timespec_get): Add to namespace
	std for C++17 and up.

From-SVN: r268879