This makes sure to not promote diagnostics about unrecognized -Wno-
options to errors and make the intent of the diagnostic clearer.

2020-02-17  Richard Biener  <rguenther@suse.de>

	PR c/86134
	* opts-global.c (print_ignored_options): Use inform and
	amend message.

	* gcc.dg/pr86134.c: New testcase.
	* gcc.dg/pr28322-2.c: Adjust.