Improve the Debug/Display impls
Improve the Debug/Display impls

nikomatsakis/lalrpop,dagit/lalrpop,tempbottle/lalrpop,dagit/lalrpop,willcrichton/lalrpop,tempbottle/lalrpop,brson/lalrpop,brson/lalrpop,timtadh/lalrpop,willcrichton/lalrpop,nikomatsakis/lalrpop,timtadh/lalrpop