Don't load nonexistent fix files for non-Monobook

Don't load nonexistent fix files for non-Monobook

Bug 14717.  I just hardcoded "&& skin == 'monobook'" in wikibits.js.  As
far as I know, no other skin actually uses fix files -- Vector, for
instance, just uses selector hacks in main-{ltr,rtl}.css as far as I
know.  Using separate files is arguably a bad idea, because it
gratuitously adds extra loads, encourages style changes to fall out of
sync, etc.  Plus, happily, the era of CSS fixes seems to be drawing to a
close -- Firefox 3.0, IE8, Opera 10, and all Safari and Chrome get by
fine with no fix files for any skin.