* include/experimental/numeric: New. Define gcd and lcm.
	* include/Makefile.am: Add new header.
	* include/Makefile.in: Regenerate.
	* testsuite/experimental/numeric/gcd.cc: New.
	* testsuite/experimental/numeric/lcm.cc: New.
	* doc/xml/manual/status_cxx2017.xml: Update status.
	* doc/html/manual/status.html: Regenerate.

From-SVN: r222724