Print intermediate results of dbg for boolean operators

[sabiwara]

Taking 40164fc one step further and support and/or boolean operators, leveraging the new list of nodes approach:

Basically we'll generate these:

# node 1
{:multi_value, {:falsy, [], nil}, result = falsy}

# node 2
(
  result = result || x
  {:multi_value, {:||, [], [{:falsy, [], nil}, {:x, [], nil}]}, result}
)

# node 3
(
  result = result && 1 / x
  {:value, {:&&, [], [...args]},, result}
)

I think __block__ would make sense too and could be done in a same way.

[sabiwara]

@josevalim for code blocks, I think we could do it if we simplify it a bit (no loss IMHO):

(a=1; b=2; a + b) |> dbg()

Current:

Code block:
(
  a = 1 #=> 1
  b = 2 #=> 2
  a + b #=> 3
)

Instead I propose:

a = 1 #=> 1
b = 2 #=> 2
a + b #=> 3

WDYT?

[josevalim]

Agreed!