Getting CommentStmt from TypeDef AST

[jcosborn]

Is there a way to get a CommentStmt out of a TypeDef? In the example below, 
`comment 3` doesn't show up in the AST tree, but is there in the repr. 
    
    
    import macros
    
    macro dump(x: typed): untyped =
      echo x.treerepr
      echo x.repr
      newEmptyNode()
    
    dump:
      ## comment 1
      type
        ## comment 2
        Foo = int ## comment 3
    

produces 
    
    
    StmtList
      CommentStmt
      TypeSection
        CommentStmt
        TypeDef
          Sym "Foo"
          Empty
          Sym "int"
      
      ## comment 1
      type
        ## comment 2
        Foo = int                   ## comment 3