title: TypeScript: unexpected import of jQuery
body: <p>Why is the <code>$</code> in the program below resolved by the compiler, given that I'm not importing jQuery?</p>
  
  <pre><code>function f () {
     $('#loadFiles').click()   // ok 
     $$('#loadFiles').click()  // error, can't find name '$$'
  }
  </code></pre>
  
  <p>I'm running the compiler (v2.0.3) as follows:</p>
  
  <ul>
  <li><code>tsc Test.ts</code>, where <code>Test.ts</code> contains only the above text;</li>
  <li>with no <code>tsconfig.json</code> or <code>typings.json</code> in the containing folder.</li>
  </ul>
  
  <p>I get that this may be related to the idiom commonly used in libraries like jQuery, but note that I'm <em>not</em> importing jQuery (as far as I know). But for some reason the compiler accepts '$' without complaining.</p>
  
  <p>Can anyone reproduce this behaviour, or suggest how I might inadvertently be picking up a definition of '$'?</p>