Parser: correct accept_with_maybe_begin_end to wrap control expression

[makenowjust]

Fixed #4488

#4488's example:

record Foo do
  def foo
    return true ? 1 : 2
  end
end

is expanded to:

struct Foo
  # ...

  def foo
    return if true
      1
    else
      2
    end
  end
end

So it causes parse error.

This PR fixes it by wrapping control expression with begin and end.

struct Foo
  # ...

  def foo
    return begin
      if true
        1
      else
        2
      end
    end
  end
end

[asterite]

Great! I didn't have time to debug the problem but the fix looks correct.

[spalladino]

Whoa, that was fast! Thanks a lot!!

[sdogruyol]

As a Japanese himself i declare @makenowjustさん "Crystal パッチモンスター" 🎉