- ruby19.y: emit correct error on "nil = 1" and friends.
+ ruby19.y: mlhs post variables "a, *b, c = ...".
+ ruby19.y: "fun (1) {}" and friends.
+ ruby19.y: mlhs arguments "def foo((a, *, p)) end".
+ ruby19.y: 99.16% coverage, 100% sans error recovery.