a litle kdevplatform view bug

[Alexander Dymo]

> #4 is irrelevant.
> Switching areas means either closing workingset (which also closes the
> document) or keeping the workingset. Note that closing a workingset closes
> all the documents in it.

Not really, try this:
- ensure Debug area has no workingset
- open Code area and open a file
- switch to Debug area, open the same file, notice the new workingset 
- modify the file
- switch to Code area
- close the file
=> you'll get no save/cancel question and the file will remain open and 
unsaved in Debug area, this is extremely confusing

This happens because workingsets only operate on views, they close/open views, 
not documents. And in #4 document is the same for two views in two different 
workingsets in two different areas.