Add -fdiagnostics-generate-patch

Add -fdiagnostics-generate-patch

gcc/ChangeLog:
	* common.opt (fdiagnostics-generate-patch): New option.
	* diagnostic.c: Include "edit-context.h".
	(diagnostic_initialize): Initialize context->edit_context_ptr.
	(diagnostic_finish): Delete context->edit_context_ptr.
	(diagnostic_report_diagnostic): Add fix-it hints from the
	diagnostic to context->edit_context_ptr, if any.
	* diagnostic.h (class edit_context): Add forward decl.
	(struct diagnostic_context): Add field "edit_context_ptr".
	* doc/invoke.texi (Diagnostic Message Formatting Options): Add
	-fdiagnostics-generate-patch.
	(-fdiagnostics-generate-patch): New item.
	* toplev.c: Include "edit-context.h".
	(process_options): Set global_dc->edit_context_ptr to a new
	edit_context if the options need one.
	(toplev::main): Handle -fdiagnostics-generate-patch by using
	global_dc->edit_context_ptr.

gcc/testsuite/ChangeLog:
	* gcc.dg/plugin/diagnostic-test-show-locus-generate-patch.c: New
	test case.
	* gcc.dg/plugin/plugin.exp (plugin_test_list): Add
	diagnostic-test-show-locus-generate-patch.c to the sources
	for diagnostic_plugin_test_show_locus.c.

From-SVN: r239965