Language extension: Parenthesize every indentation level

[Gurkenglas]

This would desugar

f = g
  h x
  i
    j k

to

f = g
  (h x)
  (i
    (j k))

and in particular it would desugar

foo = asd . evalState
  do dsa
     sda

to

foo = asd . evalState
  (do dsa
      sda)

(The solution is suboptimal because I either need an extra line only for the "do" or to start the do block on "do"'s line, but this is pretty neat in any case.)