* common.opt (fdiagnostics-show-option): No variable is needed.
* diagnostic.h (diagnostic_context): Add show_option_requested flag.
* diagnostic.c (diagnostic_initialize): Initialize show_option_requested.
(diagnostic_report_diagnostic): Test for enabled diagnostics here.
Save and restore original message format.  Use flag in context
instead of global.
(warning): Don't test for enabled warnings here.
* opts.c (common_handle_option): Handle -fdiagnostics-show-option
here.

From-SVN: r99204