Much of diagnostic-show-locus.c currently expects a diagnostic_info *,
but it only uses the rich_location and the diagnostic_t.

Change the signature of diagnostic_show_locus from:

  void
  diagnostic_show_locus (diagnostic_context *,
                         const diagnostic_info *);

to:

  void
  diagnostic_show_locus (diagnostic_context *,
                         rich_location *richloc,
                         diagnostic_t diagnostic_kind);

so that it can be used for things other than diagnostics.

Use this flexibility to add selftests for diagnostic_show_locus.

gcc/c-family/ChangeLog:
	* c-opts.c (c_diagnostic_finalizer): Update for change to
	diagnostic_show_locus.

gcc/ChangeLog:
	* diagnostic-show-locus.c (colorizer::colorizer): Replace diagnostic
	param with diagnostic_kind.
	(class colorizer): Similarly replace field m_diagnostic with
	m_diagnostic_kind.
	(colorizer::colorizer): Replace diagnostic
	param with diagnostic_kind.
	(colorizer::begin_state): Update for above field change.
	(layout::layout): Replace diagnostic param with rich_location *
	and diagnostic_kind.
	(diagnostic_show_locus): Replace diagnostic param with richloc
	and diagnostic_kind.
	(class selftest::test_diagnostic_context): New class.
	(selftest::test_diagnostic_show_locus_unknown_location): New
	function.
	(selftest::test_one_liner_simple_caret): New function.
	(selftest::test_one_liner_caret_and_range): New function.
	(selftest::test_one_liner_multiple_carets_and_ranges): New
	function.
	(selftest::test_one_liner_fixit_remove): New function.
	(selftest::test_one_liner_fixit_replace): New function.
	(selftest::test_diagnostic_show_locus_one_liner): New function.
	(selftest::diagnostic_show_locus_c_tests): Call the new test
	functions.
	* diagnostic.c (diagnostic_initialize): Initialize
	colorize_source_p, show_ruler_p and parseable_fixits_p.
	(default_diagnostic_finalizer): Update for change to
	diagnostic_show_locus.
	(diagnostic_append_note): Likewise.
	* diagnostic.h (diagnostic_show_locus): Replace
	const diagnostic_info * param with location * and diagnostic_t.

gcc/fortran/ChangeLog:
	* error.c (gfc_diagnostic_starter): Update for change to
	diagnostic_show_locus.

gcc/testsuite/ChangeLog:
	* gcc.dg/plugin/diagnostic_plugin_test_show_locus.c
	(custom_diagnostic_finalizer): Update for change to
	diagnostic_show_locus.

From-SVN: r239586