c-family/

	PR c++/31397
	* c.opt (Wsuggest-override): New option.

cp/

	PR c++/31397
	* class.c (check_for_override): Warn when a virtual function is an
	override not marked override.

gcc/

	PR c++/31397
	* doc/invoke.texi: Document -Wsuggest-override.

From-SVN: r219213