Revert r37063 "KTHMLfixes no longer loaded on skins where it doesn't exist. (bug...

Revert r37063 "KTHMLfixes no longer loaded on skins where it doesn't exist. (bug 14717)"
* Hardcoding to monobook doesn't make sense here; other skins may include such fix files
* Only addressing KHTMLfixes doesn't make sense here; there's a big pile of Opera fixes right above it which would presumably suffer the same problem

If these are required, and are required per-skin, then the skin should probably specify to the JS which ones it needs.
On the other hand, if they're not required, or can be done in a skin-independent fashion, then that should be checked.