Bugfix for checkLoaded when alias are used with relative paths

I found the following Bug:

If you alias for example jQuery with a local path /jquery.js, and also include it in the HEAD as src="jquery.js". The scripts[i].src will contain the full path of the jquery.js instead of the relative.

This causes dependant scripts loaded with l.js to reload jQuery. Reloading a script could cause problems like losing previous loaded plugins, etc.