Refactored KFileItem to use QSharedDataPointer - which means that it's now allowed to use KFileItem as a value, copying it is cheap, since it's now implicitly shared.

All the current code uses it as a pointer, which is still fine of course, but using it as a value in the future can simplify things like PreviewJob, which used to crash due to sometimes keeping a pointer to a deleted kfileitem.

Refcounting KFileItems is what Waldo has been advocating for a very long time btw, I'm glad to honor his wish after so many years :)

Michael, this is also something to keep in mind if/when rewriting KDirLister.