Directive prologues emitted outside of module wrappers

[weswigham]

Given

"use strict";
export function Relation(callback: () => new() => any): PropertyDecorator {
    return function () {
        console.log(callback());
    }
}

we presently emit:

"use strict";
define(["require", "exports"], function (require, exports) {
    function Relation(callback) {
        return function () {
            console.log(callback());
        };
    }
    exports.Relation = Relation;
});

but should emit:

define(["require", "exports"], function (require, exports) {
    "use strict";
    function Relation(callback) {
        return function () {
            console.log(callback());
        };
    }
    exports.Relation = Relation;
});

Our current emit is detrimental to the module concatenation story, as it:

• Litters the concatenated files with useless string literals.
• Breaks concatenating strict and non-strict modules together.

[mhegazy]

I believe we already have an issue for this. Could not find it though. Feel free to send a PR.