Throw error when missing commas in Array and Object expressions

Fixes #605 (closed)

Formerly:

[1 2 3]; // [1, 2, 3];

let [a b c] = []; // let [a, b, c] = [];

({ a: 1 b: 2 c: 3 }); // ({a: 1, b:2, c: 3});

let { a b c } = {}; // let { a, b, c } = {};

let [...rest, a] = []; // let [...rest_0] = [];

[...[],]; // [...[],,];

All of these cases save the last should throw (it was simply parsing incorrectly). Now they do:

[1 2 3]
// Error: unexpected token
// __2__ 3

let [a b c] = [];
// Error: unexpected token
// __b__ c

({ a: 1 b: 2 c: 3 })
// Error: unexpected token
// __b__ : 2 c : 3

let { a b c } = {};
// Error: unexpected token
// __b__ c

let [...rest, a] = [];
// Error: Rest element must be last element in array
// , a

[...[],]; // [...[]];