proxy: bind() use rewritten apply if native function, otherwise original to avoid unnecessary deproxying

[ikreymer]

before this fix, something like:

let window = <proxy override>
let document = <proxy override>
...
let d = document;
let w = window;

let f = function(w, d) {
}.bind(this)

would result in w and d in f being de-proxied. This fixes this unneeded deproxying