allow `else` and `=>` keyword in `case`
allow `else` and `=>` keyword in `case`

koba-e964/picrin,picrin-scheme/picrin,ktakashi/picrin,leavesbnw/picrin,dcurrie/picrin,omasanori/picrin,koba-e964/picrin,picrin-scheme/picrin,omasanori/picrin,ktakashi/picrin,leavesbnw/picrin,leavesbnw/picrin,ktakashi/picrin,koba-e964/picrin,dcurrie/picrin