FIX: Transform default values correctly in destructuring

[0xe]

Default values for destructuring assignments weren't transformed correctly. Partially addresses #1641.

For example, all of these expressions with default values were not being evaluated correctly:

function a() { return 12;};  function b([x = a()] = []) { return x }; b()
function a() { return 12;};  function b([x = a()] = [1]) { return x }; b()
function a() { return 12;};  function b([x = 1] = [a()]) { return x }; b()
var a = { p1: { p2: 121}}; function b([x = a.p1.p2] = []) { return x }; b()

function a() { return 12;};  function b({x = a()} = {}) { return x }; b()
function a() { return 12;};  function b({x = a()} = {x: 1}) { return x }; b()
var a = { p1: { p2: 121}}; function b({x = a.p1.p2} = {}) { return x }; b()
function a() { return 12;};  function b({x = 1} = {x: a()}) { return x }; b()

[rbri]

the number of fixed tests is really impressive.good job.

[gbrail]

This is great -- thanks!