Optimize >> and << in compiled JS

[jfmengels]

This effectively changes Elm's core >> and << from (roughly)

(<<) g f x =
  g (f x)

-- to

(<<) g f =
  \x ->
    g (f x)

In other words, the composition functions are now wrapped in F2 instead of F3, which yields much better performance because it gets applied using A2(composeL, f, g) in practice.

[jfmengels]

Reflects the changes done in elm/core#1145