cache/core_component.php dependent on filesystem ordering

The classmap array in core_component.php is ordered based on filesystem ordering. This can be a problem when the cache file is first created in a clustered environment, since each cluster node may be trying to create a different version of the file. There is a sha1 hash comparison in core_component::init() which should let the caching work in a clustered setup, but that fails due to differing ordering of the classmap.

The fix is simply to sort the classmap before writing to the file.