Fix type of module.require

Although it has the same type as the global require function, the global
require function isn't a type (constructor).  So update the type of
module.require to match it.  This fixes the following warning:

./core.js:76: WARNING - Bad type annotation. Unknown type require
 * @type {require}
          ^

Signed-off-by: Kevin Locke <[email protected]>

core.js

@@ -73,7 +73,7 @@ var exports;
 module.exports;
 
 /**
- * @type {require}
+ * @type {function(string)}
  */
 module.require;