Add TOKEN enum entries for EOF, decode error, drop, and none

assets/parser.d.erb

@@ -78,6 +78,10 @@ class <%= classname %>
             TOKEN_<%= token.c_name %> = <%= index %>,
 <%   end %>
 <% end %>
+            TOKEN_EOF = <%= TOKEN_EOF %>,
+            TOKEN_DECODE_ERROR = <%= TOKEN_DECODE_ERROR %>,
+            TOKEN_DROP = <%= TOKEN_DROP %>,
+            TOKEN_NONE = <%= TOKEN_NONE %>,
         }
 
         static immutable string TokenNames[] = [