[Review Only] Brackets polyfill support

This is an *attempt* to implement functionality from pull request #7231, and also work with minified builds, but it's not yet working. Brackets works (based on very minimal usage), but the polyfill is not applied.

**To create and run a minified build locally:**
1. [Setup Grunt](https://github.com/adobe/brackets/wiki/Grunt-Setup)
2. Run `grunt build`
3. Hold down `Shift` key when starting Brackets
4. When prompted for `index.html`, use `src/dist/index.html`

**Testing Polyfill Mechanism**
The polyfill added to `utils/Compatibility.js` in this PR is for IE10, so I added a `trimAll()` polyfill to that file locally so this could be tested in current desktop Brackets (i.e. CEF3 Chrome):

```JS
if (!String.prototype.trimAll) {
    String.prototype.trimAll = function () { return this.replace(/\s+/g, ""); };
}
window.console.log("utils/Compatibility loaded!");
```

I then created a `trimTest` extension where contents of `main.js` is:

```JS
/*jslint vars: true, plusplus: true, devel: true, nomen: true, indent: 4, maxerr: 50 */
/*global define, brackets */

define(function (require, exports, module) {
    "use strict";

    var CommandManager  = brackets.getModule("command/CommandManager"),
        Menus           = brackets.getModule("command/Menus");


    var testString = " this is a test string ";
    
    function trimTest() {
        if (testString.trimAll) {
            alert("testString: '" + testString + "';\ntestString.trimAll(): '" + testString.trimAll() + "'");
        } else {
            alert("trimAll is not defined");
        }
    }

    Menus.getMenu("debug-menu").addMenuItem(
        CommandManager.register("Trim Test", "trimTest.trimTest", trimTest)
    );
});
```

**To test:**
Use Debug > Trim Test

**success:** `alert()` says: testString: ' this is a test string '; testString.trimAll(): 'thisisateststring' 

**failure:** `alert()` says: "trimAll is not defined"