+/**
+ * Issue a diagnostic message.
+ * Format types:
+ * %E expression_t const*
+ * %K token_t const*
+ * %k token_kind_t
+ * %#k va_list*, char const*
+ * %N entity_t const*
+ * %#N entity_t const*
+ * %P source_position_t const*
+ * %Q unsigned (qualifier)
+ * %S string_t const*
+ * %T type_t const*
+ * %#T type_t const*, symbol_t const*
+ * %Y symbol_t const*
+ */