parser support anon iterators

tests/parser/tdomulttest.nim

@@ -0,0 +1,17 @@
+discard """
+  file: "tdomulttest.nim"
+  output: "555\ntest\nmulti lines\n99999999\nend"
+  disabled: true
+"""
+proc foo(bar, baz: proc (x: int): int) =
+  echo bar(555)
+  echo baz(99999999)
+
+foo do (x: int) -> int:
+  return x
+do (x: int) -> int:
+  echo("test")
+  echo("multi lines")
+  return x
+
+echo("end")