* (bug 10316) Prevent inconsistent cached skin settings in gen=js by setting the...

* (bug 10316) Prevent inconsistent cached skin settings in gen=js by setting the intended skin directly in the URL.

Not sure whether the global 'skin' and 'stylepath' settings should be removed from the gen=js or from the inline vars, but this fixes the inconsistency between them.
It also fixes the inconsistent use of skin-specific .js files (MediaWiki:Monobook.js loaded for wrong skin, etc).
By passing the skin name directly in the gen=js, we ensure both that we have the correct skin information cached
and that you'll get the JS along with useskin= on an HTML page.

Normally useskin= prevents caching, but RawPage handles its own caching headers, so this doesn't cause any problems here. Doesn't seem to be a performance problem in my quick ab testing either.