diagnostics: eliminate diagnostic_kind_count

diagnostics: eliminate diagnostic_kind_count

No functional change intended.

gcc/ChangeLog:
	* diagnostic.cc (diagnostic_context::check_max_errors): Replace
	uses of diagnostic_kind_count with simple field acesss.
	(diagnostic_context::report_diagnostic): Likewise.
	(diagnostic_text_output_format::~diagnostic_text_output_format):
	Replace use of diagnostic_kind_count with
	diagnostic_context::diagnostic_count.
	* diagnostic.h (diagnostic_kind_count): Delete.
	(errorcount): Replace use of diagnostic_kind_count with
	diagnostic_context::diagnostic_count.
	(warningcount): Likewise.
	(werrorcount): Likewise.
	(sorrycount): Likewise.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>