`prettify` fails on `do` notation

[cscherrer]

Call:

prettify(
    quote
        map(1:N) do n
            f(n)
        end
    end
)

Result:

:(map(1:N) do n
      f
      n
  end)

Expected:

:(map(1:N) do n
      f(n)
  end)

System info: Manjaro Linux Julia Version 0.7.0-rc2.0 Commit 78540cba4c (2018-08-02 19:14 UTC) MacroTools v0.4.2