Adding in blank files for backcompat with anything manually including them.

Fixes some errors that have cropped up like:

```
Warning:
require_once(/home/private/public_html/wp-content/plugins/jetpack/module
s/featured-content/featured-content.php) [function.require-once]:
failed to open stream: No such file or directory in
/home/private/public_html/wp-content/plugins/jetpack/modules/theme-tools
.php on line 54
```

Introduced in
https://github.com/Automattic/Jetpack/commit/7a3e6bf205e08c2ffa4a2b4514f
6513a875c4d51