[if] condition indentation change for Jane Street and an interesting OCaml parser edge case

[pszilagyi]

Sorry, I know this is switching back and forth, but we changed our mind on the indentation for [if] conditions. I hope it's easy to switch that one case back.

We also noticed an interesting edge case in the OCaml grammar for top-level [let] interacting with [function]. We added a test case to edge-cases.ml indicating how OCaml parses it, which is not at all intuitive. (This is low priority for us.)

(We also removed one discouraged style from our tests, which is not important.)

Thanks for your help!