PR bootstrap/63699
	PR bootstrap/63750

	* system.h: Include <string> before "safe-ctype.h"
	* wide-int.h (wi::smin, wi::smax, wi::umin, wi::umax): Prefix
	calls to min/max with wi namespace.
	* ipa-chkp.c: Don't include <string>.

	* plugin.cc: Don't include <string>.

From-SVN: r217342